David Sang and Graham Jones Solutions for Chapter: Electric Current, Potential Difference and Resistance, Exercise 9: Questions

A calculator is powered by a $3.0 \mathrm{V}$ battery. The calculator's resistance is $20\mathrm{k}\Omega$. Calculate the power transferred to the calculator.

An energy-efficient light bulb is labelled $\text{'}230 \mathrm{V},15 \mathrm{W}\text{'}$. This means that when connected to the $230 \mathrm{V}$ mains supply it is fully lit and changes electrical energy to heat and light at the rate of $15 \mathrm{W}$. Calculate the current in the bulb when fully lit.

An energy-efficient light bulb is labelled $\text{'}230 \mathrm{V},15 \mathrm{W}\text{'}$. This means that when connected to the $230 \mathrm{V}$ mains supply it is fully lit and changes electrical energy to heat and light at the rate of $15 \mathrm{W}$. Calculate:

(b) Its resistance when fully lit.

Calculate the resistance of a $100 \mathrm{W}$ light bulb that draws a current of $0.43 \mathrm{A}$ from a power supply.