Question:
In an electrical circuit two resistors of 2Ω and 4Ω respectively are connected in series to a 6V battery. The heat dissipated by 4Ω resistor in 5 s will be
(a) 5 J
(b) 10 J
(c) 20 J
(d) 30 J
Solution:
(c).
Explantion: Total resistance of the circuit, $\mathrm{R}$
$=2 \Omega+4 \Omega=6 \Omega$
Voltage, $\mathrm{V}=6 \mathrm{~V}$
$\therefore$ Current in the circuit, $\mathrm{I}=\frac{\mathrm{V}}{\mathrm{R}}=\frac{6}{6}=1 \mathrm{~A}$
Heat dissipated by $4 \Omega$ resistor in $5 s=I^{2} R t$
$=1 \times 4 \times 5=20 \mathrm{~J}$