Surroundings 19153

A heating element with a resistance of 1.6 Ω is used to heat the car's rear glass. The body is connected to the battery in the car, which has a voltage of 12 V.

a) What is the power input of the heating element?
b) How much heat does the heating element give off to its surroundings if it works for 1 hour?

Correct answer:

P =  90 W
Q =  324 kJ

Step-by-step explanation:

$$\begin{gathered} R=1.6\Omega \\ U=12\text{V} \\ I=U/R=12/1.6=\frac{15}{2}=7.5\text{A} \\ P=U\cdot I=12\cdot 7.5=90\text{W} \end{gathered}$$

$$\begin{gathered} t=3600\text{s} \\ {Q}_1=P\cdot t=90\cdot 3600=324000\text{J} \\ Q=Q_1/1000=324000/1000=324\text{kJ} \end{gathered}$$

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