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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- A. Impedance
- B. Conductivity
- C. Admittance
- D. Reactance
Explanation: Conductivity measures how readily a material carries current and is the reciprocal of resistivity, with units of siemens per metre.
Correct answer: Conductivity- A. No current flows
- B. Current is maximum
- C. Internal resistance is infinite
- D. Load resistance is zero
Explanation: The lost volts inside the cell are the current multiplied by the internal resistance, so only when the current is zero, that is on open…
Correct answer: No current flows- A. Quarter
- B. Half
- C. Zero
- D. 4 times
Explanation: Resistance is proportional to length for a given cross section and material, so quadrupling the length quadruples the resistance.
Correct answer: 4 times- A. 1/C
- B. 1/K
- C. 1/A
- D. 1/s
Explanation: The coefficient is the fractional change in resistivity per unit rise in temperature, so the resistivity units cancel and only reciprocal…
Correct answer: 1/K- A. source of EMF
- B. conductor
- C. resistor
- D. capacitor
Explanation: Internal resistance is the resistance inside a cell or other source of EMF, caused by its electrolyte and internal materials.
Correct answer: source of EMF- A. Become zero
- B. Is halved
- C. Is doubled
- D. )D. remains same
Explanation: Resistivity is a property of the material and depends mainly on its nature and temperature, not on the wire's length or cross-sectional…
Correct answer: )D. remains same- A. 1 S
- B. 1.5 S
- C. 2 S
- D. 5 S
Explanation: Conductance is the reciprocal of resistance: G = 1/R = 1/(0.5 ohm) = 2 S.
Correct answer: 2 S- A. Resistance
- B. Voltage
- C. Current
- D. None of these
Explanation: The ohm (Ω) is the SI unit of electrical resistance, defined by R = V/I, so 1 Ω = 1 V/A.
Correct answer: Resistance29. If electrical conductivity increases with the increase of temperature of a substance, then it is a:
- A. Semiconductor
- B. Conductor
- C. Insulator
- D. None of the above
Explanation: In a semiconductor, increasing temperature releases more charge carriers, so electrical conductivity increases.
Correct answer: Semiconductor- A. Gas only
- B. Liquid only
- C. Solid only
- D. All of the above
Explanation: Young's modulus is the ratio of tensile or compressive stress to the corresponding strain, and it describes the elastic deformation of…
Correct answer: Solid only- A. The resistance of each of them increases.
- B. The resistance of each of them decreases.
- C. The resistance of copper decreases and that of germanium increases.
- D. The resistance of copper increases and that of germanium decreases
Explanation: Copper is a metal, so cooling reduces lattice vibrations and decreases its resistance.
Correct answer: The resistance of copper decreases and that of germanium increases.- A. 105 ohm metre
- B. 106 ohm metre
- C. 107 ohm metre
- D. 108 ohm metre
Explanation: Insulators have very large resistivities, and the standard approximate value used in this classification is about 10^8 ohm metre, much…
Correct answer: 108 ohm metre- A. a most sensitive galvanometer is used
- B. a steady voltage cell is used
- C. the balance point is close to the middle of the wire
- D. a high resistance box is used in one of its gap
Explanation: In a slide-wire bridge, accuracy is greatest when the balance point is near the middle, because the two wire lengths and their measurement…
Correct answer: the balance point is close to the middle of the wire34. Which one of the following physical quantities does not have the dimensions of force per unit area ?
- A. Stress
- B. Strain
- C. Youngs modulus
- D. Pressure
Explanation: Stress, Young's modulus and pressure are all force per unit area, with dimensions M L^-1 T^-2.
Correct answer: Strain- A. MLT-2
- B. ML-2T-1
- C. ML-1T-2
- D. ML-T-1
Explanation: Stress = force/area. Force has dimensions M L T^-2 and area has dimensions L², so stress has dimensions M L T^-2 / L² = M L^-1 T^-2.
Correct answer: ML-1T-2- A. Rubber
- B. Steel
- C. Glass
- D. Copper
Explanation: Elasticity in this comparison is measured by Young's modulus, and steel has a much larger Young's modulus than rubber, copper or ordinary…
Correct answer: Steel- A. 100 watt
- B. 200 watt
- C. 300 watt
- D. 60 watt
Explanation: For bulbs designed for the same voltage, R = V²/P, so resistance is inversely proportional to rated power.
Correct answer: 300 watt- A. zero almost
- B. infinite almost
- C. no prediction at all
- D. may increase or decrease
Explanation: In the ideal textbook model for a metallic conductor, thermal vibrations vanish as the temperature approaches 0 K, so its resistance…
Correct answer: zero almost- A. hyperbola
- B. ellipse
- C. parabola
- D. straight line
Explanation: Ohm's law is V = IR, so for constant resistance a graph of potential difference V in volts (V) against current I in amperes (A) is a…
Correct answer: straight line- A. 40 W bulb
- B. 60 W blub
- C. 100 W blub
- D. all will burn equally brightly
Explanation: At the same rated voltage of 220 V, each bulb's resistance is R = V²/P, so the 40 W bulb has the greatest resistance.
Correct answer: 40 W bulb