Question

Question 15
In an electrical circuit two resistors of 2 $\Omega$ and 4 $\Omega$ respectively are connected in series to a 6 V battery. The heat dissipated by the 4 $\Omega$ resistor in 5 s will be

(a) 5 J
(b) 10 J
(c) 20 J
(d) 30 J

Answer 1

(c) 20 J

Equivalent resistance for resistors connected in series, $R=R_1+R_2=2+4=6\Omega$
Voltage, V=6V
$\Rightarrow I=\frac{V}{R}=\frac{6}{6}=1A$
Heat dissipated by the 4 $\Omega$ resistor in 5 s is given by,
$Heat=I^{2}Rt=(1{)}^2\times 4\times 5=20J$