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## electric current

### 2. Series 9. Year - E. afternoon tea

Establish the resistance of electric spiral boiler

**Hint:** Warm up water and measure the evolution of its temperature in time.

### 1. Series 9. Year - 3. plate capacitor

A capacitor formed by two parallel metal plates of area $S$ each placed in a distance $l_{1}$ one from another are charged at the voltage $U_{b}$. What work must be performed to move the plates apart to distance $l_{2}$, if we

- had disconnected,
- hadn’t disconnected

the battery..