NDA (I) 2025 General Ability Test · Question 127 of 150

Correct — C, 12 V. Potential difference is the work done per unit charge: V = W/q. Here V = 24 J divided by 2 C = 12 V.

• (a)48 V — This multiplies work by charge (24 x 2) instead of dividing — the wrong operation.
• (b)6 V — This divides by 4 rather than by the 2 C of charge; V = 24/2 = 12 V, not 6 V.
• (d)0.08 V — This divides charge by work (2/24) — the formula inverted; it should be work divided by charge.

The electric potential difference between two points is the work done in moving a unit positive charge from one point to the other: V = W/q, measured in volts, where one volt equals one joule per coulomb. It is the 'push' that drives current around a circuit.

The only step is to apply V = W/q correctly. The wrong options come from inverting the formula (q/W) or multiplying instead of dividing. Keep the units in view: joules divided by coulombs give volts.

• Potential difference V = W/q; its unit, the volt (V), equals one joule per coulomb (J/C).
• Moving 2 C when 24 J of work is done gives V = 24/2 = 12 V.
• One volt is the potential difference that does 1 joule of work in moving 1 coulomb of charge.
• Potential difference (not current) is what a voltmeter measures across two points.

• Divide work by charge (W/q); do not multiply them or invert the formula.
• Potential difference is measured in volts by a voltmeter connected in parallel.

Numerical items give work and charge (or current and resistance) and ask for the potential difference using V = W/q or V = IR.

No directly related past PYQ was found.

• practice — not a real PYQ

  The work done in moving a charge of 5 C through a potential difference of 4 V is

  • (a)0.8 J
  • (b)1.25 J
  • (c)20 J
  • (d)9 J

  Answer(c) 20 J — W = qV = 5 x 4 = 20 J.

• practice — not a real PYQ

  The SI unit of electric potential difference is the

  • (a)ampere
  • (b)ohm
  • (c)volt
  • (d)coulomb

  Answer(c) volt — one volt equals one joule per coulomb.