Paper 4 Electromagnetic Induction Drills

Q1 Magnet and Coil Investigation

A student drops a small magnet through a coil connected to a data logger.

1. State what quantity the data logger should record. [1]
2. Explain why two opposite pulses may be seen. [2]
3. State two changes that would increase the peak induced emf. [2]

Q2 Sliding Rod Practical Model

A conducting rod of active length $l=0.250\mathrm{m}$ moves at speed $v$ perpendicular to its length and to a uniform magnetic field. The induced emf $\mathcal{E}$ is measured for several speeds.

$v$/$\mathrm{m}{\mathrm{s}}^{-1}$	0.40	0.80	1.20	1.60	2.00	2.40
$\mathcal{E}$/V	0.051	0.099	0.151	0.198	0.252	0.299

1. Plot a graph of $\mathcal{E}$ against $v$ and draw a best-fit straight line. [5]
2. Determine the gradient and state its unit. [2]
3. Use $\mathcal{E}=Blv$ to determine the magnetic flux density $B$. [2]
4. Explain whether the graph supports $\mathcal{E}\propto v$. [2]
5. State one method of measuring $v$ and one precaution that improves the validity of the model. [2]