Question

# 1 . Mercury has a mass of 3.30×1023 kg and a radius of 2.44×106 m.

Find Mercury's gravitational field strength.
Show your work (formula, substitution, and answer (rounded correctly and with the appropriate unit)) .

2 . A small Styrofoam ball has a 2.26 nC charge (2.26×10-9 C). Find the electric field strength 5.00 cm (0.0500 m) from the ball.
Show your work (formula, substitution, and answer (rounded correctly and with the appropriate unit)) .

3 . A 12 V battery is connected to a resistor, a light bulb, and a buzzer. What are the energy conversions that occur in the circuit?

4. desk top computer plugs into the wall socket at 120V and draws an average current of 2.10 A. How much energy (in kWh) does the computer use each day assuming that it is never turned off?
Show your work, including formulae and substitutions and express your answer rounded correctly and with the appropriate units.

5 . A cell phone battery has 9.00×10-3 kWh of energy stored in it. If the battery runs at 3.20 V and draws an average of 0.375 A of current, how long will the battery last?
Show your work, including formulae and substitutions and express your answer rounded correctly and with the appropriate units.

6 . Three 12 Ω resistors are connected in parallel and then connected to a 6.0 V battery. Find the resulting current.
Show your work (formula, substitution, answer rounded correctly and with the appropriate unit. This is a two part question.

7 . For the circuit described in the previous question, the total current was measured to be 1.48 A. Is this an unexpected result? Explain your answer. Show your calculations.

8 . A group of students found an old DC electric motor in a box. They were looking for a small generator they could use to power their computer while they were out camping. Explain how they might with the motor they found.

9 . A 100 MW power station generates energy at 26.0 kV. The power lines must carry only 200 A of current to be efficient enough. To what voltage must the potential be increased?
Show your work (formula, substitution, answer rounded correctly and with the appropriate unit).

10 . Electric transmission is accomplished at very high voltages when long distances are being covered. This reduces the currents involved and makes the transmission line far more efficient. On the other hand, we don't want extremely high voltages in our houses!
Describe how utility companies can lower the voltages to reasonable levels and still keep their systems efficient.