A car battery has an e.m.f. of $12 \mathrm{V}$ and an internal resistance of $0.04\Omega$. The starter motor draws a current of $100 \mathrm{A}$.

(b) Each head lamp is rated as $\text{'}12\mathrm{V},36\mathrm{W}\text{'}$. Calculate the resistance of a headlamp.

A car battery has an e.m.f. of $12 \mathrm{V}$ and an internal resistance of $0.04\Omega$. The starter motor draws a current of $100 \mathrm{A}$.

(c) To what value will the power output of each headlamp decrease when the starter motor is in operation? (Assume that the resistance of the headlamp remains constant.)

Determine the range of $V_{\text{out }}$ for the circuit in Figure as the variable resistor $R_2$ is adjusted over its full range from $0\Omega$ to $40\Omega$. (Assume the supply of e.m.f. $10 \mathrm{V}$ has negligible internal resistance.)

What is the voltage across the $3.0\mathrm{k}\Omega$ resistor in Figure when the light intensity is 10 lux?

The circuit shown in Figure produces a decreasing output voltage when the light intensity increases. How can the circuit be altered to produce an increasing output voltage as the light intensity increases?

An LDR used as a sensor.

Design a circuit using the thermistor in Figure that uses a cell of $10 \mathrm{V}$ and produces an output voltage of $5 \mathrm{V}$ at $50°\mathrm{C}$. Explain whether the voltage output of your circuit increases or decreases as the temperature rises.

Variation of resistance with temperature.

To make a potentiometer, a driver cell of e.m.f. $4.0 \mathrm{V}$ is connected across a $1.00 \mathrm{m}$ length of resistance wire.

(a) What is the potential difference across each $1 \mathrm{cm}$ length of the wire? What length of wire has a p.d. of $1.0 \mathrm{V}$ across it?