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Free Current Electricity MCQs with Answers

1,052 Current Electricity MCQs from Physics, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.

Steady current relates charge flow to potential difference, resistance and resistivity, including how temperature changes a conductor's resistance. Sources with internal resistance have terminal voltage below their emf when delivering current, and maximum power output occurs under a specific load condition rather than at zero resistance.

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Steady CurrentResistance and ResistivityTemperature Coefficient of ResistivityInternal Resistance of SourcesMaximum Power Output
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1,052 questions Β· page 32 of 53

621. A metal cube with sides of length "π‘Ž" has electrical resistance 𝑅 between opposite faces. What is the resistance between the opposite faces of a cube of the same metal with sides of length 3π‘Ž?

  • A. 9𝑅
  • B. 3𝑅
  • C. R/3
  • D. 𝑅/9

Explanation: the resistance can be found by the relation R=pL/A p(resistivity) In this case L=a and A=a2 soR=p 1/aWhen L=3a then A=9a2So R=p 1/3a Hence…

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Correct answer: R/3

622. Four resistors are connected in a square as shown. The resistance may be measured between any two junctions. Between which two junctions is the measured resistance greatest?

  • A. P and Q
  • B. Q and S
  • C. R and S
  • D. S and P

Explanation: Formula for total resistance in a parallel circuit will be used 1/Rt=1/R1 + 1/R2

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Correct answer: Q and S

623. The power loss 𝑃 in a resistor is calculated using the formula: 𝑃 =𝑉2/R The uncertainty in the potential difference 𝑉 is 3% and the uncertainty in the resistance 𝑅 is 2%. What is the uncertainty in 𝑃?

  • A. 4%
  • B. 7%
  • C. 8%
  • D. 11%

Explanation: β€’The fractional error in V would be3Γ—2=6β€’The fractional error in R would be2β€’So the fractional error of power would be equal to the sum of…

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Correct answer: 8%

624. When we are measuring the internal resistance of a cell by potentiometer, the emf of the battery must be greater than the :

  • A. Emf of the cell
  • B. P.D in the circuit
  • C. Current in the cell
  • D. Current in the circuit

Explanation: The emf of the battery in the potentiometer experiment should be greater than the emf of the cell to be determined because The fall of…

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Correct answer: Emf of the cell

625. A car battery has EMF of 12 volts and internal resistance 5 x 10^-2 ohm. If it draws 60 ampere current, then terminal voltage of the battery will be:

  • A. 5 volts
  • B. 3 volts
  • C. 15 volts
  • D. 9 volts

Explanation: E= V+IrV = E-Ir = 12-(60)(5Γ—10-2) = 9 volts

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Correct answer: 9 volts

626. Two wires A and B are made of the same material. Wire A has a length of I, and a diameter of R while wire B has a length of 2L and a diameter of R/2. If the two wires are stretched by the same force, the elongation in A divided by the elongation in B is:

  • A. β…›
  • B. ΒΌ
  • C. 4
  • D. 8

Explanation: Wires made of the same material have the same Young Modulus.Hence, option A is the correct choice.

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Correct answer: β…›

627. The resistance of a device is designed to change with temperature. What is the device?

  • A. A light dependent resistor
  • B. A potential divider
  • C. A semiconductor diode
  • D. A thermistor

Explanation: The resistance of a device thermistor is designed to change with temperature.

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Correct answer: A thermistor

628. When will 1 C of charge pass a point in an electrical circuit?

  • A. When 1A moves through a voltage of 1V
  • B. When a power of 1W is used for 1s
  • C. When the current is 5mA for 200s
  • D. When the current is 10A for 10s

Explanation: The formula used is Q = I x t Putting in the values, we get 1C as charge when Option C is used.

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Correct answer: When the current is 5mA for 200s

629. A cell of internal resistance 2.0Ω and electromotive force (e.m.f) 1.5V is connected to a resistor of resistance 3.0Ω. What is the potential difference across the 3.0Ω resistor?

  • A. 5V
  • B. 1.2V
  • C. 0.9V
  • D. 0.6V

Explanation: Rtotal = Internal resistance of the cell + Resistance of the external resistorRtotal = 2.0Ω + 3.0ΩRtotal = 5.0ΩCalculate the current (I)…

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Correct answer: 0.9V

630. Two lamps are connected in series to a 250 V power supply. One lamp is rated 240 V, 60 W, and the other rated 10 V, 2.5 W. Which statement most accurately describes what happens?

  • A. Both lamps light at less than their normal brightness
  • B. Both lamps light at their normal brightness
  • C. Only the 240 V lamp lights
  • D. The 10 V lamp blows

Explanation: Since One lamp is rated 240 V, 60 W This means that for the lamp to operate normally, there should be a p.d.

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Correct answer: Both lamps light at their normal brightness

631. Three resistors of 6 ohms each, can be connected in all possible ways. The highest value of resistance that can be obtained (in ohms) is:

  • A. 2 Ohms
  • B. 4 Ohms
  • C. 9 Ohms
  • D. 18 Ohms
  • E. 36 Ohms

Explanation: If we connect all three in series, combined resistance will be 6+6+6=18(Series combination always gives the highest combined resistance)If…

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Correct answer: 18 Ohms

632. The temperature coefficient of a semiconductor is negative because:

  • A. Resistance increases with an increase in temperature
  • B. Resistance decreases with an increase in temperature
  • C. Resistance decreases with decrease in temperature
  • D. Resistance is independent of temperature change

Explanation: A negative coefficient for a material means that its resistance decreases with an increase in temperature.

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Correct answer: Resistance decreases with an increase in temperature

633. Ohm's law applies to:

  • A. Semiconductors
  • B. Vacuum tubes
  • C. Carbon resistors
  • D. Conductors

Explanation: According to Ohm's law, Resistance of a conductor is directly proportional to its length.

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Correct answer: Conductors

634. In a series circuit, current remains?

  • A. Same
  • B. Different
  • C. Variable
  • D. Zero

Explanation: In series circuits, current remains the same while voltage divides. In a parallel circuit, current divides while voltage is the same.

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Correct answer: Same

635. In a parallel circuit, the voltage remains:

  • A. Same
  • B. Different
  • C. Variable
  • D. Zero

Explanation: In a parallel circuit, the voltage stays constant and current varies. Applying Kirchoff's voltage law: The sum of the voltages in a loop…

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Correct answer: Same

636. The flow of charges produces:

  • A. Current only
  • B. Magnetic field only
  • C. Electric field only
  • D. All of the above

Explanation: Electric current is the rate of flow of charges. In electric circuits this charge is often carried by electrons moving through a…

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Correct answer: All of the above

637. Electric current may be defined as:

  • A. Rate of flow of charge
  • B. Rate of flow of momentum
  • C. Rate of flow of power
  • D. Rate of flow of energy

Explanation: Option A is correct. Electric current is defined as the rate of flow of electric charge through a conductor.

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Correct answer: Rate of flow of charge

638. _ relationship exists between current and voltage in terms of Ohm's law.

  • A. Non linear
  • B. Varying
  • C. Linear
  • D. Alternating

Explanation: V=IRLinear: The correct answer is this one. Ohm's law states that the relationship between current (I) and voltage (V) is linear for a…

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Correct answer: Linear

639. A current of 20.0A flows through a battery with an e.m.f of 6.20 V. If the internal resistance of the battery is 0.01, what is the terminal voltage?

  • A. 6.40V
  • B. 31.0V
  • C. 1.24V
  • D. 6.00V

Explanation: V = e.m.f - (I * Rinternal)where:V is the terminal voltage,e.m.f is the electromotive force (voltage) of the battery,I is the current…

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Correct answer: 6.00V

640. A wire of resistance 3.0 Ξ© is stretched to twice its original length. The resistance of the new wire will be:

  • A. 1.5 Ξ©
  • B. 3.0 Ξ©
  • C. 6.0 Ξ©
  • D. 12.0 Ξ©

Explanation: R = PL/A where p is density, L is length and A is area.Resistance R = ρℓ / Aβ„“' = 2 β„“ β‡’ A' = A / 2R' = ρ [2 β„“ / (A / 2)] = 3R = 3 Γ— 4Ξ© = 12Ξ©

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Correct answer: 12.0 Ξ©
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