Basic Electrical interview questions

150 questions with answers (EEE-001 to EEE-150). Try each one aloud before reading the answer.

Circuit Theory

EEE-001 · What are Kirchhoff's laws?

KCL: the algebraic sum of currents at a node is zero (conservation of charge). KVL: the algebraic sum of voltages around any closed loop is zero (conservation of energy).

EEE-002 · What is power factor?

Power factor is cos φ, the cosine of the angle between voltage and current, equal to real power ÷ apparent power (P/S). A low PF means more current is needed for the same useful power.

EEE-003 · What are the voltage and current relations in star and delta connections?

In star, V_L = √3 V_ph and I_L = I_ph. In delta, V_L = V_ph and I_L = √3 I_ph. Line quantities lead or lag phase quantities by 30° in a balanced system.

EEE-004 · State Ohm's law.

At constant temperature, the current through a conductor is proportional to the voltage across it: V = IR, where R is resistance in ohms (Ω).

EEE-005 · What is the difference between active, reactive and apparent power?

Active power P = VI cos φ (W) does useful work. Reactive power Q = VI sin φ (VAR) oscillates between source and fields. Apparent power S = VI (VA), with S² = P² + Q².

EEE-006 · What is the RMS value of an AC waveform?

The RMS value is the equivalent DC value that produces the same heating in a resistor. For a sine wave, V_rms = V_m/√2 ≈ 0.707 V_m.

EEE-007 · What is impedance?

Impedance Z = R + jX is the total opposition to AC current, combining resistance and reactance. Its magnitude is |Z| = √(R² + X²), measured in ohms.

EEE-008 · What are inductive and capacitive reactance?

Inductive reactance X_L = 2πfL rises with frequency. Capacitive reactance X_C = 1/(2πfC) falls with frequency. Both are measured in ohms.

EEE-009 · State Thevenin's theorem.

Any linear two-terminal network can be replaced by a single voltage source V_th (open-circuit voltage) in series with an impedance Z_th (seen from the terminals with independent sources deactivated).

EEE-010 · State Norton's theorem.

Any linear two-terminal network can be replaced by a current source I_N (short-circuit current) in parallel with an impedance Z_N, which equals Z_th.

EEE-011 · What is resonance in an RLC circuit?

Resonance occurs when X_L = X_C, at f₀ = 1/(2π√(LC)). A series RLC circuit then has minimum impedance (equal to R), and the current is in phase with voltage.

EEE-012 · What is the form factor of a waveform?

Form factor = RMS value ÷ average value. For a sine wave it is 1.11.

EEE-013 · What is the superposition theorem?

In a linear network with several independent sources, the response in any element equals the sum of responses due to each source acting alone, with others replaced by their internal impedances.

Electromagnetics

EEE-014 · State Faraday's law of electromagnetic induction.

The EMF induced in a circuit equals the rate of change of flux linkage: e = −N dΦ/dt. The negative sign reflects Lenz's law.

EEE-015 · State Lenz's law.

The induced current flows in a direction that opposes the change in magnetic flux that produced it.

EEE-016 · What is magnetic flux density?

Flux density B is flux per unit area, B = Φ/A, measured in tesla (T = Wb/m²).

EEE-017 · What is reluctance?

Reluctance S = l/(μA) is the opposition of a magnetic circuit to flux, analogous to resistance. Its unit is ampere-turns per weber (AT/Wb).

EEE-018 · What is magnetomotive force (MMF)?

MMF is the driving force for flux in a magnetic circuit, F = NI, measured in ampere-turns. Flux Φ = F/S.

EEE-019 · What is permeability?

Permeability μ = μ₀μᵣ measures how easily a material supports magnetic flux. μ₀ = 4π × 10⁻⁷ H/m; μᵣ is the relative permeability.

EEE-020 · What is hysteresis?

Hysteresis is the lag of flux density B behind magnetizing force H in a ferromagnetic material. The area of the B-H loop represents energy lost per cycle per unit volume.

EEE-021 · What is Fleming's left-hand rule used for?

It gives the direction of force on a current-carrying conductor in a magnetic field: forefinger = field, middle finger = current, thumb = motion. It applies to motors.

EEE-022 · What is Fleming's right-hand rule used for?

It gives the direction of induced EMF in a conductor moving in a magnetic field: forefinger = field, thumb = motion, middle finger = induced current. It applies to generators.

EEE-023 · What is self-inductance?

Self-inductance L is the property of a coil that opposes changes in its own current by inducing an EMF, e = −L di/dt. Unit: henry (H).

EEE-024 · What is mutual inductance?

Mutual inductance M links two coils so that a changing current in one induces EMF in the other, e₂ = −M di₁/dt. M = k√(L₁L₂), where k is the coupling coefficient.

EEE-025 · What is retentivity and coercivity?

Retentivity is the residual flux density remaining after H is removed. Coercivity is the reverse H needed to bring B to zero.

EEE-026 · What is the force on a current-carrying conductor in a magnetic field?

F = BIL sin θ, where B is flux density, I current, L active length and θ the angle between conductor and field.

Transformers

EEE-027 · What is a transformer?

A static device that transfers AC energy between circuits by mutual induction, changing voltage and current levels while keeping frequency the same.

EEE-028 · What is the turns ratio of a transformer?

The turns ratio a = N₁/N₂ = V₁/V₂ = I₂/I₁ for an ideal transformer.

EEE-029 · State the EMF equation of a transformer.

E = 4.44 f N Φ_m, where f is frequency, N turns and Φ_m peak core flux in webers.

EEE-030 · What is the difference between core-type and shell-type transformers?

In core type, windings surround the core limbs. In shell type, the core surrounds the windings, giving better mechanical support and lower leakage reactance.

EEE-031 · What is the function of transformer oil?

It insulates the windings and carries heat away from the core and windings to the tank and radiators.

EEE-032 · What is a step-up and step-down transformer?

A step-up transformer has N₂ > N₁ and raises voltage. A step-down transformer has N₂ < N₁ and lowers voltage.

EEE-033 · What is an autotransformer?

A transformer with a single winding, part of which is common to primary and secondary. It is smaller and cheaper for ratios near 1 but gives no electrical isolation.

EEE-034 · What is the function of a conservator tank?

It accommodates expansion and contraction of oil with temperature, keeping the main tank full and limiting the oil surface exposed to air.

EEE-035 · What is a breather in a transformer?

A breather contains silica gel that absorbs moisture from air entering the conservator as oil contracts. Silica gel changes colour when saturated.

EEE-036 · What is the purpose of a tap changer?

It changes the turns ratio to regulate output voltage. Off-load tap changers need de-energization; on-load tap changers (OLTC) operate under load.

EEE-037 · What is a Buchholz relay?

A gas-actuated relay fitted between the main tank and conservator of oil-filled transformers. It alarms on slow gas accumulation and trips on a sudden oil surge from internal faults.

EEE-038 · What is transformer efficiency?

Efficiency η = output/(output + iron loss + copper loss). Maximum efficiency occurs when copper loss equals iron loss.

EEE-039 · What is voltage regulation of a transformer?

Regulation = (V_no-load − V_full-load)/V_full-load × 100%, measured at the secondary. Lower regulation means a steadier output voltage.

DC Machines

EEE-040 · What is the function of a commutator in a DC machine?

It acts as a mechanical rectifier, converting the alternating EMF in armature conductors to DC at the brushes (generator) or reversing coil current to give unidirectional torque (motor).

EEE-041 · State the EMF equation of a DC generator.

E = PΦNZ/(60A), where P is poles, Φ flux per pole, N speed in rpm, Z armature conductors and A parallel paths.

EEE-042 · What are the types of DC motors by excitation?

Separately excited, shunt, series and compound (cumulative or differential). Self-excited types draw field current from the armature supply.

EEE-043 · What is back EMF in a DC motor?

Back EMF E_b is the EMF induced in the rotating armature that opposes the supply voltage: V = E_b + I_a R_a. It limits armature current.

EEE-044 · What is the difference between lap and wave winding?

Lap winding has A = P parallel paths, suiting high-current, low-voltage machines. Wave winding has A = 2, suiting high-voltage, low-current machines.

EEE-045 · What is the function of brushes?

Brushes, usually carbon, make sliding contact with the commutator to carry current between the rotating armature and the external circuit.

EEE-046 · What is armature reaction?

The effect of armature MMF on the main field flux. It distorts the field (cross-magnetizing) and can weaken it (demagnetizing), shifting the magnetic neutral axis.

EEE-047 · What are interpoles?

Small poles placed between main poles, with windings in series with the armature. They neutralize reactance voltage in the commutating zone and improve commutation.

EEE-048 · State the torque equation of a DC motor.

T = (PΦZ I_a)/(2πA) N·m, so T ∝ Φ I_a.

EEE-049 · What is the speed equation of a DC motor?

N ∝ E_b/Φ = (V − I_a R_a)/Φ. Speed falls with increasing flux and rises when flux is weakened.

EEE-050 · Why is a starter needed for a DC motor?

At standstill, E_b = 0, so armature current I_a = V/R_a would be very large. A starter adds series resistance, cut out as speed and back EMF build up.

EEE-051 · Where are DC series motors used?

In traction, cranes and hoists, because they give very high starting torque (T ∝ I_a² before saturation).

Induction Machines

EEE-052 · What is the working principle of an induction motor?

A rotating stator field induces EMF and current in the rotor conductors. The rotor current interacts with the field to produce torque, and the rotor follows the field at slightly less than synchronous speed.

EEE-053 · What is synchronous speed?

N_s = 120f/P rpm, where f is supply frequency and P the number of poles. For 50 Hz and 4 poles, N_s = 1500 rpm.

EEE-054 · What is slip?

Slip s = (N_s − N_r)/N_s. Typical full-load slip is about 2–6% for standard motors.

EEE-055 · What is the difference between squirrel-cage and slip-ring rotors?

A squirrel-cage rotor has short-circuited bars and is rugged and cheap. A slip-ring (wound) rotor has a three-phase winding brought out to slip rings, allowing external resistance for starting and speed control.

EEE-056 · What is the frequency of rotor current?

f_r = s f. At standstill (s = 1) it equals supply frequency; at full load it is only a few hertz.

EEE-057 · Why is a single-phase induction motor not self-starting?

A single-phase winding produces a pulsating field, equivalent to two equal fields rotating in opposite directions, so net starting torque is zero.

EEE-058 · What are the methods of starting a three-phase induction motor?

Direct-on-line (DOL), star-delta, autotransformer, rotor resistance (slip-ring only), soft starter and VFD.

EEE-059 · What is a capacitor-start induction motor?

A single-phase motor with an auxiliary winding in series with a capacitor, giving a near-90° phase shift and high starting torque. A centrifugal switch disconnects the auxiliary circuit near rated speed.

EEE-060 · How do you reverse a three-phase induction motor?

Swap any two of the three supply lines. This reverses the phase sequence and the direction of the rotating field.

EEE-061 · What is the typical starting current of a DOL-started induction motor?

About 5–8 times full-load current, depending on motor design.

EEE-062 · What are the losses in an induction motor?

Stator and rotor copper losses, core loss, friction and windage, and stray load losses.

EEE-063 · What is an induction generator?

An induction machine driven above synchronous speed (negative slip). It delivers active power but draws reactive power for magnetization from the grid or capacitors.

Synchronous Machines

EEE-064 · What is a synchronous machine?

An AC machine whose rotor runs at synchronous speed N_s = 120f/P, with a DC-excited field (or permanent magnets) locked to the rotating armature field.

EEE-065 · What is an alternator?

A synchronous generator that converts mechanical energy into AC electrical energy, usually with a rotating field and stationary armature.

EEE-066 · Why is the armature stationary and the field rotating in large alternators?

High-voltage armature windings are easier to insulate and connect when stationary, and only low-power DC excitation passes through slip rings or a brushless exciter.

EEE-067 · What is the difference between salient-pole and cylindrical rotors?

Salient-pole rotors have projecting poles, large diameter and suit low-speed hydro sets. Cylindrical (round) rotors are long, small diameter and suit high-speed steam and gas turbines.

EEE-068 · What is synchronous reactance?

X_s = X_l + X_a, the sum of armature leakage reactance and the fictitious reactance representing armature reaction. Synchronous impedance Z_s = R_a + jX_s.

EEE-069 · What is the EMF equation of an alternator?

E_ph = 4.44 K_p K_d f Φ T_ph, where K_p is pitch factor, K_d distribution factor and T_ph turns per phase.

EEE-070 · What is synchronization of an alternator?

Connecting an alternator to a live bus only when its voltage, frequency, phase sequence and phase angle match the bus.

EEE-071 · Why is a synchronous motor not self-starting?

The rotating stator field reverses relative to the stationary rotor poles every half cycle, so the average torque is zero. Damper windings or a pony motor bring it near synchronous speed first.

EEE-072 · What is a damper winding?

Short-circuited bars in the rotor pole faces. They provide induction-motor starting torque and damp hunting oscillations.

EEE-073 · What is a synchronous condenser?

An over-excited synchronous motor running without mechanical load, used to supply reactive power and regulate voltage.

EEE-074 · What is the excitation system of an alternator?

The source of DC field current, such as a DC exciter, a brushless AC exciter with rotating rectifiers or a static thyristor exciter. The AVR controls it.

EEE-075 · What is hunting in a synchronous machine?

Oscillation of rotor speed about synchronous speed after a sudden load or supply change. Damper windings suppress it.

Power Generation

EEE-076 · What are the main types of power plants?

Thermal (coal, gas, oil), hydroelectric, nuclear, and renewables such as wind, solar PV, solar thermal, biomass and geothermal.

EEE-077 · What is a base-load plant?

A plant that runs continuously near full output to meet the minimum constant demand, such as large coal, nuclear or run-of-river hydro plants.

EEE-078 · What is a peak-load plant?

A plant that runs only during peak demand and can start quickly, such as gas turbines, pumped storage and reservoir hydro.

EEE-079 · What is load factor?

Load factor = average load ÷ maximum demand over a period. A higher load factor lowers the cost per unit generated.

EEE-080 · What is plant capacity factor?

Capacity factor = actual energy produced ÷ (rated capacity × time). It shows how fully the plant is utilized.

EEE-081 · What is the Rankine cycle?

The thermodynamic cycle of steam power plants: water is pumped to boiler pressure, boiled to steam, expanded in a turbine and condensed back to water.

EEE-082 · What is the function of a condenser in a thermal plant?

It condenses exhaust steam at low pressure (vacuum), increasing the turbine's enthalpy drop and efficiency and recovering pure feed water.

EEE-083 · What is the power available from a hydro plant?

P = ρ g Q H η, where ρ is water density, g gravity, Q flow rate (m³/s), H head (m) and η overall efficiency. Roughly P(kW) ≈ 9.81 Q H η.

EEE-084 · What is the power available from wind?

P = ½ ρ A v³ C_p, where A is swept area and v wind speed. C_p is limited by the Betz limit of 16/27 ≈ 0.593.

EEE-085 · What is a solar PV cell?

A semiconductor p-n junction that converts light directly into DC electricity through the photovoltaic effect.

EEE-086 · What is a pumped storage plant?

A hydro plant that pumps water to an upper reservoir during low demand and generates during peak demand, acting as large-scale energy storage.

EEE-087 · What is diversity factor?

Diversity factor = sum of individual maximum demands ÷ maximum demand of the whole system. It is always ≥ 1.

EEE-088 · What is a combined-cycle power plant?

A plant where gas turbine exhaust heat is recovered in a heat-recovery steam generator to drive a steam turbine, raising overall efficiency well above a simple-cycle plant.

Transmission & Distribution

EEE-089 · Why is AC used for power transmission?

Transformers step AC voltage up and down easily. Higher voltage means lower current for the same power, which cuts I²R losses and conductor size.

EEE-090 · What are the main parameters of a transmission line?

Series resistance R, series inductance L, shunt capacitance C and shunt conductance G, all distributed along the line.

EEE-091 · How are transmission lines classified by length?

Short (below about 80 km, capacitance ignored), medium (about 80–250 km, lumped π or T model) and long (above about 250 km, distributed parameters).

EEE-092 · What is ACSR conductor?

Aluminium Conductor Steel Reinforced: aluminium strands for conductivity around a steel core for tensile strength.

EEE-093 · What is the function of insulators on overhead lines?

They support conductors on towers and insulate them from the earthed structure. Types include pin, suspension (disc string), strain and post insulators.

EEE-094 · What is sag in an overhead line?

The vertical dip of a conductor below the straight line joining its supports. For level supports, sag ≈ wL²/(8T), where w is weight per unit length, L span and T tension.

EEE-095 · What is skin effect?

The tendency of AC current to concentrate near the conductor surface, raising effective resistance. It increases with frequency and conductor size.

EEE-096 · What is the difference between radial and ring main distribution?

A radial system feeds loads from one end, so a fault interrupts all downstream consumers. A ring main feeds loads from two directions, improving reliability.

EEE-097 · What is a feeder, distributor and service main?

A feeder carries power from the substation to distribution points without tappings. Distributors have tappings for consumers. Service mains connect a distributor to a consumer's premises.

EEE-098 · What is a substation?

A facility that transforms voltage, switches circuits and houses protection equipment between generation, transmission and distribution.

EEE-099 · What is the purpose of a stay wire on a pole?

It counteracts unbalanced horizontal conductor tension at line ends, angles and turns, keeping the pole upright.

EEE-100 · What are underground cables made of?

A conductor (copper or aluminium), insulation (such as XLPE or PVC), a metallic screen or sheath, armouring and an outer serving.

EEE-101 · What is the efficiency of a transmission line?

η = receiving-end power ÷ sending-end power × 100%. Losses are mainly I²R in the conductors plus corona at high voltage.

Protection & Switchgear

EEE-102 · What is the difference between a fuse and an MCB?

Both protect against overcurrent. A fuse element melts and must be replaced. An MCB trips through thermal and magnetic elements and can be reset.

EEE-103 · What is switchgear?

The combination of switches, circuit breakers, fuses, isolators, relays and associated equipment used to control, protect and isolate electrical equipment.

EEE-104 · What is a circuit breaker?

A switching device that can make, carry and break normal currents and automatically interrupt fault currents when signalled by a relay.

EEE-105 · What is the difference between an isolator and a circuit breaker?

An isolator is an off-load disconnector for visible isolation during maintenance. A circuit breaker can interrupt load and fault current.

EEE-106 · What is an RCD or RCCB?

A residual current device trips when the difference between phase and neutral currents (earth leakage) exceeds a set value, typically 30 mA for shock protection.

EEE-107 · What is a protective relay?

A device that senses abnormal conditions such as overcurrent, overvoltage or impedance change, and signals a circuit breaker to trip.

EEE-108 · What are the essential qualities of a protection system?

Selectivity, speed, sensitivity, reliability, stability and simplicity.

EEE-109 · What is an overcurrent relay?

A relay that operates when current exceeds a pickup setting. It may be instantaneous, definite-time or inverse-time.

EEE-110 · What is an arc in a circuit breaker?

A conducting plasma column that forms between separating contacts and keeps current flowing until it is extinguished, usually at a current zero.

EEE-111 · What arc-quenching media are used in circuit breakers?

Air, oil, SF₆ gas and vacuum.

EEE-112 · What is a lightning arrester?

A surge arrester that diverts lightning and switching surges to earth while presenting high impedance at normal voltage. Modern types use metal-oxide (ZnO) blocks.

EEE-113 · What is a current transformer used for in protection?

A CT steps primary current down to a standard secondary value (commonly 1 A or 5 A) for relays and meters, and isolates them from high voltage.

EEE-114 · What is a zone of protection?

The section of the system covered by a particular protective scheme. Adjacent zones overlap around circuit breakers so no part is unprotected.

Power Electronics

EEE-115 · What is power electronics?

The use of semiconductor switches to control and convert electrical power, such as AC-DC, DC-DC, DC-AC and AC-AC conversion.

EEE-116 · What is an SCR?

A silicon controlled rectifier is a four-layer PNPN thyristor that conducts when forward-biased and triggered by a gate pulse, and stays on until current falls below holding current.

EEE-117 · What is the difference between latching current and holding current?

Latching current is the minimum anode current needed to keep the SCR on immediately after gate pulse removal. Holding current is the minimum current to remain on afterwards; latching current is higher.

EEE-118 · What is a rectifier?

A converter that changes AC to DC. It can be uncontrolled (diodes), half-controlled or fully controlled (thyristors).

EEE-119 · What is an inverter?

A converter that changes DC to AC at the desired voltage and frequency.

EEE-120 · What is a chopper?

A DC-DC converter that switches a DC supply on and off to produce a variable average DC output, such as buck and boost converters.

EEE-121 · What is a cycloconverter?

An AC-AC converter that changes frequency directly without a DC link, typically producing a lower output frequency.

EEE-122 · What is an IGBT?

An insulated gate bipolar transistor combines MOSFET voltage-controlled gate input with BJT-like low conduction loss. It is widely used in medium and high power inverters.

EEE-123 · What is duty cycle?

Duty cycle D = T_on/T, the fraction of the switching period a switch is on.

EEE-124 · What is a freewheeling diode?

A diode connected across an inductive load that gives load current a path when the switch turns off, preventing high voltage spikes.

EEE-125 · What is PWM?

Pulse width modulation varies the width of switching pulses to control average output voltage or synthesize a sinusoidal output in inverters.

EEE-126 · What is the output voltage of an ideal buck converter?

V_o = D V_in, where D is duty cycle, so the output is always less than or equal to the input.

Electrical Measurements

EEE-127 · What instrument measures current and how is it connected?

An ammeter, connected in series with the load. It must have very low resistance.

EEE-128 · What instrument measures voltage and how is it connected?

A voltmeter, connected in parallel across the element. It must have very high resistance.

EEE-129 · What is a megger?

An insulation resistance tester that applies a high DC voltage (such as 500 V, 1 kV or 5 kV) and reads resistance in megohms.

EEE-130 · What is a wattmeter?

An instrument that measures active power. The electrodynamometer type has a current coil in series and a pressure coil in parallel with the load.

EEE-131 · What is an energy meter?

A meter that measures energy consumed in kWh. Older types are induction disc meters; modern ones are electronic or smart meters.

EEE-132 · What is a multimeter?

A portable instrument that measures voltage, current and resistance, and often continuity, capacitance and frequency.

EEE-133 · What is a clamp meter?

A meter with a split-core jaw that measures current by clamping around a conductor without breaking the circuit.

EEE-134 · What is the difference between accuracy and precision?

Accuracy is closeness to the true value. Precision is repeatability of readings, regardless of whether they are correct.

EEE-135 · What is a Wheatstone bridge used for?

Measuring medium resistances (about 1 Ω to 100 kΩ) accurately. At balance, R₁/R₂ = R₃/R₄.

EEE-136 · What is a potential transformer?

A PT or VT steps high voltage down to a standard secondary voltage (commonly 110 V line-to-line) for meters and relays.

EEE-137 · What is a moving-iron instrument?

An instrument where a soft-iron vane moves in the field of a coil. It reads both AC and DC because deflecting torque is proportional to I².

EEE-138 · What is a PMMC instrument?

A permanent magnet moving coil instrument with torque proportional to current. It reads DC only, has a linear scale and high accuracy.

Electrical Safety, Wiring & Drives

EEE-139 · What is earthing?

Connecting the non-current-carrying metal parts of equipment, or the system neutral, to the general mass of earth through a low-resistance path.

EEE-140 · What is the difference between earthing and bonding?

Earthing connects parts to earth. Bonding connects metallic parts together so they stay at the same potential, preventing dangerous touch voltages between them.

EEE-141 · What are the common types of earth electrodes?

Pipe, rod, plate and strip electrodes, chosen by soil type and required resistance.

EEE-142 · What is the colour code for single-phase wiring under IEC conventions?

Brown for line, blue for neutral and green-yellow for protective earth.

EEE-143 · What is an electric drive?

A system that controls the speed, torque and position of an electric motor, comprising the power source, converter, motor, controller and load.

EEE-144 · What is a VFD?

A variable frequency drive controls AC motor speed by varying supply frequency and voltage, usually through a rectifier, DC link and PWM inverter.

EEE-145 · What is a DOL starter?

A direct-on-line starter connects the motor straight to full supply voltage through a contactor with overload protection. It is used for small motors.

EEE-146 · What is a star-delta starter?

It starts the motor in star (phase voltage reduced by 1/√3) and switches to delta near running speed. Starting current and torque fall to one-third of DOL values.

EEE-147 · What is an overload relay?

A relay, usually thermal or electronic, that trips a motor contactor when sustained current exceeds rated value, protecting against overheating.

EEE-148 · What is a contactor?

An electrically operated switch designed for frequent switching of power circuits such as motors, controlled by a coil.

EEE-149 · What is lockout-tagout (LOTO)?

A safety procedure that isolates energy sources and locks and tags them so equipment cannot be energized while work is being done.

EEE-150 · Why is electric shock dangerous even at low currents?

Current through the body, not voltage, causes harm. Currents of tens of milliamperes across the chest can cause ventricular fibrillation.

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