The diagram shows a circuit with the key k open

Electricity and Magnetism (10)

The diagram above shows a circuit with the key k open.

Calculate:

  1. the resistance of the circuit when the key k is open.
  2. the current drawn from the cell when the key k is open.
  3. the resistance of the circuit when the key k is closed.
  4. the current drawn from the cell when the key k is closed.

Answer

(i) R = 5 + 0.5 = 5.5 Ω

(ii) I = 3.3/5.5 = 3/5 = 0.6 A

(iii) R1 = (5×5)/(5+5) = 2.5 Ω

∴ R = 2.5 + 0.5 = 3 Ω

(iv) I = 3.3/3 = 1.1 A

  • Exam Year: 2019