Chapter 11 Electricity Questions-07
QUESTIONS
1. What determines the rate at which energy is delivered by a current?
Show Answer
Answer
The rate of consumption of electric energy in an electric appliance is called electric power. Hence, the rate at which energy is delivered by a current is the power of the appliance.
2. An electric motor takes 5 A from a 220 V line. Determine the power of the motor and the energy consumed in $2 h$.
Show Answer
Answer
Power $(P)$ is given by the expression, $P=V I$
Where,
Voltage, $V=220 V$
Current, $I=5 A$
$P=220 \times 5=1100 W$
Energy consumed by the motor $=Pt$
Where,
Time, $t=2 h=2 \times 60 \times 60=7200 s$
$\therefore P=1100 \times 7200=7.92 \times 10^{6} J$
Therefore, power of the motor $=1100 W$
Energy consumed by the motor $=7.92 \times 10^{6} J$
