 IB Fields - Electric and Magnetic

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1. Two identical charges q are seperated by a distance r. The charges will repel with a force F.

If the distance between the charges is increased to 2r and both charges increased to 2q, the force will now be

• A. F/4
• B. F/2
• C. F
• D. 2F

2. An electronvolt is a unit of

• A. work done
• B. charge
• C. voltage
• D. current

3. Which of these diagrams correctly shows the electric field strength between these two charges? 4. Electric field strength is defined as

• A. the force per unit charge on a small positive test charge
• B. the force per unit charge on a small negative test charge
• C. the force per unit charge on a unit positive charge
• D. the force per unit charge on a unit negative charge

Four metal spheres P,Q, R and S are arranged in a square as shown. Each one has a charge of q or -q or zero. 5. The electric field at a point in the centre of the square will be zero if
• A. All charges are positive
• B. P and Q are positive, R and S are negative
• C. P and Q are positive, R and S have no charge
• D. P is positive, Q R and S have no charge

6. A current flows in a metal wire when attached to a cell. Which of the following correctly describes the charge carriers in the wire and their movement?

 Charge carrier sign Moves round the circuit from A + positive to negative B - positive to negative C + negative to positive D - negative to positive

A 2 mC charge is held between two charged plates. The plates have an electric field of 40 'units' between them. 7. The unit of electric field strength E is

• A. NC
• B. NV
• C. NC-1
• D. NV-1

8. The force on the charge due to the field will be
• A. 20N
• B. 80N
• C. 0.02N
• D. 0.08N

9. If the voltage between the 2 plates is 2kV, the work done in moving the charge from plate to plate is

• A. 1J
• B. 4J
• C. 1eV
• D. 4eV

10. Two metal wires A and B have identical currents flowing in them . Wire A has a smaller cross-sectional area than B. This means wire A must also

• A. have charge carriers with a larger charge than B
• B. be longer than B
• C. have fewer charge carriers per unit volume than B
• D. have a higher charge drift velocity than B