Electricity and Magnetism

Capacitors and Transformers

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=0t = 0. If the capacitor is initially uncharged, then which of the following graphs best represent the current in the circuit at time tt?

Two identical parallel plate capacitors are connected to a battery with the switch SS closed. When SS is opened and the free space between the capacitors is filled with a material of dielectric constant KK, 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 μF 10 \ \mu \text{F} is charged to 50 μC 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 dd between them is doubled?

Capacitors in series and parallel Capacitors in series and parallel

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


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