Question

how many joules does a lamp marked 12 volts, 24 w consumed in an hour . And also what is the current?

Answer 1

Given data:

* The voltage given is 12 volts.

* The value of the power given is 24 Watt.

* The time till which the lamp is used is,

`\begin{gathered} t=1\text{ hr} \\ t=60*60\text{ s} \\ t=3600\text{ s} \end{gathered}`

Solution:

(a). The energy consumed by the lamp in time t is,

`E=P* t`

where P is the power of lamp, t is the time, and E is the energy consumed,

Substituting the known values,

`\begin{gathered} E=24*3600 \\ E=86400\text{ J} \\ E=86.4*10^3\text{ J} \\ E=86.4\text{ kJ} \end{gathered}`

Thus, the energy consumed by the lamp in 1 hour is 86.4 kJ.

(b). The power of the lamp in terms of voltage and current is,

`\begin{gathered} P=VI \\ I=(P)/(V) \end{gathered}`

where P is the power, V is the voltage and I is the current,

Substituting the known values,

`\begin{gathered} I=(24)/(12) \\ I=2\text{ A} \end{gathered}`

Thus, the current flowing through the lamp is 2 A.