Electricity and Magnetism

Capacitors and Transformers: Level 2-3 Challenges

A transformer has 40 turns in its primary coil and 20 turns in its secondary coil. Is it a step-up transformer or a step-down transformer?

Image Credit Wikimedia Commons Brian Green

The switch in the above figure is closed at $$t = 0$$. If the capacitor is initially uncharged, then which of the following graphs best represent the current in the circuit at time $$t$$?

Two identical parallel plate capacitors are connected to a battery with the switch $$S$$ closed. When $$S$$ is opened and the free space between the capacitors is filled with a material of dielectric constant $$K$$, the ratio of the total electrostatic energies stored in both capacitors, after and before the introduction of the dielectric, is $$\text{__________}$$.

A parallel plate capacitor of capacitance $$10 \ \mu \text{F}$$ is charged to $$50 \ \mu \text{C}$$ using a battery, and is then disconnected from the circuit. How much energy (in microjoules) is required to pull apart the plates such that the distance $$d$$ between them is doubled?

Capacitors in series and parallel

Each capacitor in the above diagram has capacitance $$C$$. What is the equivalent capacitance?

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