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Question
The figure shows a circuit. When the circuit is switched on, the ammeter reads 0.5 A.
(i) Calculate the value of the unknown resistor R.
(ii) Calculate the charge passing through the 3 Ω resistor in 120 s.
(iii) Calculate the power dissipated in the 3 Ω resistor.
Solution
(i) We know, V = IR'
⇒ 6 = 0.5 × R'
⇒ R' = 12 Ohm
∵ R' = 3 + R
⇒ 12 = 3 + R
⇒ R = 9 Ohm
(ii) Charge, q = i t
⇒ q = 0.5 × 120 = 60 Coulomb
(iii) Power dissipation, p = i2R
p = 0.52 × 3 = 0.75 Watt
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