Paper 4 Alternating Current Generators Drills

Q1 Model Generator Investigation

A model generator has a coil of $N=100$ turns and area $A=4.00\times 10^{-3}{\mathrm{m}}^2$. Its peak emf ${\mathcal{E}}_0$ is measured at several rotation frequencies $f$.

$f$/Hz	5.0	10.0	15.0	20.0	25.0	30.0
${\mathcal{E}}_0$/V	2.5	5.1	7.5	10.1	12.4	15.1

1. Plot a graph of ${\mathcal{E}}_0$ against $f$ and draw a best-fit straight line. [5]
2. Determine the gradient and state its unit. [2]
3. Using ${\mathcal{E}}_0=NBA\omega$ and $\omega =2\pi f$, determine $B$. [3]
4. Explain whether the data support ${\mathcal{E}}_0\propto f$. [2]
5. State one source of scatter and one variable that must be controlled. [2]

Q2 Comparing Slip Rings and Commutator

1. State the observable difference between outputs from slip rings and a split-ring commutator. [2]
2. Explain the role of connections in producing the difference. [2]
3. State one practical safety issue when rotating coils are used. [1]