Current Electricity

Section A: Objective Type Questions

  1. The drift velocity of electrons in a metallic conductor is proportional to: (a) applied voltage (b) resistance of the conductor (c) square of the electric field strength (d) inverse of the relaxation time

  2. Which of the following is not a unit of electrical power? (a) watt (b) joule/second (c) volt/ampere (d) kilowatt-hour

  3. A wire of resistance R is cut into two pieces, each having a resistance of R/2. The pieces are then connected in parallel. The equivalent resistance of the combination is: (a) R/4 (b) R/2 (c) R (d) 2R

  4. A voltmeter has a resistance of 20,000 ohms. It is used to measure the potential difference across a resistance of 1,000 ohms. The reading on the voltmeter will be: (a) 0.05 V (b) 0.5 V (c) 5 V (d) 50 V

  5. When a current of 2 A flows through a wire for 10 s, the charge passing through any cross-section of the wire during this time is: (a) 2 C (b) 5 C (c) 10 C (d) 20 C

Section B: Short Answer Type Questions 6. Derive an expression for the equivalent resistance of three resistors connected in series.

  1. State and explain Kirchhoff's second law for a closed loop in an electrical circuit.
  2. Define the term 'electric potential' and explain its physical significance.
  3. Derive an expression for the energy stored in a capacitor.
  4. A wire of length 1 m and resistance 2 ohms is stretched to double its length. Calculate the new resistance of the wire.

Section C: Long Answer Type Questions 11. Derive an expression for the resistance of a conductor in terms of its length, cross-sectional area, and resistivity.

  1. Explain the working principle of a potentiometer and how it can be used to measure the emf of a cell.
  2. Derive an expression for the energy stored in an inductor.
  3. State and explain Joule's law of heating. How does it affect the efficiency of electrical appliances?
  4. Two resistors of resistances 3 ohms and 6 ohms are connected in parallel. A cell of emf 12 V and negligible internal resistance is connected across the combination. Calculate the current flowing through the 3 ohm resistor and the power dissipated in the 6 ohm resistor.