Target: 10 Questions in 10 minutes

An IB Physics data booklet is helpful

 1. Electric potential energy Ep is defined as...

  • A. the work done to assemble the system from infinite separation
  • B. the work done per unit mass to assemble the system from infinite separation
  • C. the work done per unit charge to assemble the system from infinite separation
  • D. the work done to move the parts of the system to infinite separation

2+3: Two charges +Q are separated by a distance r. There is a repulsive force F acting between the 2 charges as shown. The potential energy of the system is E.

Two charges +Q separated by a distance r

  

2. What is the electric potential energy if the charges are moved to a distance of ½ r?

  • A. ¼ E
  • B. ½ E
  • C. 2 E
  • D. 4 E

3. What change to the original system shown in the diagram would result in the potential being 6E?

  • A. Increase the original distance to 3r.
  • B. Decrease the original distance by a factor of 3.
  • C. Keep the original distance, but increase both charges to + 3 Q.
  • D. Keep the original distance, but increase both charges to + √6 Q.

4. Electric potential V is zero at infinity (away from all charged objects). What are the units for V, and is it a scalar or vector quantity?

  units scalar or vector?
A JC-1 (volts) scalar
B JC-1 (volts) vector
C CJ-1 (volts) scalar
D CJ-1 (volts) vector

5-8. A hollow metal sphere is charged to a high potential. The diagram below shows the electric field lines around the sphere.

hollow sphere with electric field

5. A student is asked to add lines to the diagram to show the equipotential lines.

Which of the following statements about the equipotential lines is true?
  • A. they are circular and equally spaced
  • B. they are circular with varying spacing
  • C. they are radial
  • D. they pass through the centre of the diagram

6. Which of the following statements describes the field strength and the electric potential inside the hollow sphere?
field strength
potential
A
constant non-zero value
zero
B
constant non-zero value
constant non-zero value
C
zero
constant non-zero value
D
zero
zero

Q7+8: The graph shows how the electric potential varies with distance from a point charge:

electric potential vs distance graph

7. The gradient of this graph at any point is equal to the...

  • A. electric potential energy
  • B. electric field strength
  • C. work done per unit charge moving from that point to infinity
  • D. total charge in coulombs

8. Using data from the graph, what work is done moving a small test charge of +2 nC from a distance of 2 m to 4 m?

  • A. +0.1 µJ
  • B. -0.1 µJ
  • C. +0.2 µJ
  • D. -0.2 µJ

9. Which of these diagrams best shows the shape of equipotential surfaces around two positively charged spheres?

equipotential surfaces aound binary stars

10. At which point in this diagram is the electrical potential due to the 2 charges approximately equal to zero?
two charges procuding electric field