Physics PSPM2 Paper1_40 Objective

Three charges + q, + Q and – Q are placed at the corners of an equilateral triangle. The net force on charge + q due to the other two charges is FIGURE 1

• A. vertically up.

• B. vertically down

• C. horizontal to the left.

• D. horizontal to the right.

2. FIGURE 2 shows a charge 2Q is located at the origin while a second charge – Q is located at x = a . Where should a third positive charge be placed so that the net force on the charge is zero?

• A. x < 0

• B. 0 < x < a

• C. x > a

• D. x < 0 OR 0 < x < a

3. A positive charge that is in an electric field E experiences a force that is

• A. perpendicular to E .

• B. zero because the speed is zero.

• C. in the opposite direction to E .

• D.in the same direction as E .

4. The concept of electric potential difference is most closely associated with

• A. the mechanical force on an electron.

• B. the resistance of a certain specified column of mercury.

• C. the charge on one electron.

• D. the work per unit quantity of charge.

5. In a uniform electric field, a proton has

• A. a constant velocity in the direction of the field.

• B. a constant velocity in the direction opposite to that of the field.

• C. a constant acceleration in the direction of the field.

• D. a constant acceleration in the direction opposite to that of the field.

6. As the voltage in the circuit is increased, the capacitance

• A. increases.

• B. decreases.

• C.does not change.

• D.does none of these.

7. The capacitance of a parallel–plate capacitor

• A. decreases if a dielectric is placed between its plates.

• B. is independent of the distance between the plates.

• C. has units of J C⁻¹ .

• D. is independent of the charge on the capacitor.

8. If 4.70 × 10¹⁶ electrons pass a point in a wire every second, what is the current in the wire?

A.4.70 mA

B.3.67 mA

C.2.95 mA

D.7.52 mA

• A

• B

• C

• D

9. The resistivity of any given metal

A. depends on its temperature.

B. varies linearly with temperature.

C. has units of Ohm–meter.

D. is described by all of the above.

• A

• B

• C

• D

10. The graph in FIGURE 3 below shows the potential difference across a resistor as a function of the current through the resistor. The slope of the resulting curve represents

• A. power

• B. resistance

• C. e.m.f.

• D. charge