1. In the circuit shown, a 20Ω resistor is inside 100 g of water that is surrounded by an insulator.

If the water is initially at 10◦C how long will it take for the temperature to rise to 58◦C?

2. In the circuit shown, find:

(a) The current in the 3Ω resistor.

(b) The unkown emf’s E1 and E2.

(c) The resistance R. Note the three currents given.

3. A long copper rod of radius R carries a constant current I, with the current density (current

per unit area) J→ uniform over its cross section. Compute the value of the magnetic field B(r)

at all values of radius r from the center of the rod (there are two regions: r < R> R).

4. A semi-circular wire of radius R, carrying a current I, is placed in a constant magnetic field