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Capacitors and Transformers

Capacitors are devices that accumulate voltage in separated electric charges, but their mechanism and mathematics can describe thermal insulation and the discharge of lightning from cloud to ground.

Level 2-3

         

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

Capacitors in series and parallel

Each capacitor in the above diagram has capacitance \(C\). What is the equivalent capacitance?

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