Self-Test: Electromagnetism (Forces) Test #2
Suggested Time: 65 minutes

1.

In which diagram would an external magnetic field, B , cause two current-carrying wires to move towards one another?

2.

When there is no current in the solenoids, the electron beam in the cathode ray tube strikes the screen at the origin O.

In order to move the beam to position P, which solenoid is used and what is the direction of the current applied?

3.

Which of the following devices commonly uses a solenoid?

A. kettle

B. battery

C. television set

D. incandescent bulb

4.

An electron, travelling with a constant velocity, enters a region of uniform magnetic field. Which of the following is not a possible pathway?

5. A bar magnet is at rest, next to a fixed coil. When switch S is closed, the bar magnet will move

A. to the left.

B. to the right.

C. up the page.

D. down the page.

6.

Which of the following diagrams best represents the magnetic field in the region between the two permanent magnets?

7.

In which diagram would the current-carrying conductor experience a magnetic force out of the page?

8.

A coil of 25 turns of wire is suspended by a thread. When a current flows through the coil, the tension in the thread is reduced by 4.0 ´10-2 N.

What are the magnitude and direction of the current?

9. The diagram shows current I flowing in a circular coil located in a magnetic field.

The magnetic force acting on the coil will tend to cause it to

A. expand.

B. contract.

C. move up the page.

D. move down the page.

10.

An aircraft whose wingspan is 15 m carries a static charge of 0.60 C. It travels at 240 m/s perpendicular to a 1.5 ´ 10-4 T magnetic field. What magnetic force does the aircraft experience?

A. 0.022 N

B. 0.060 N

C. 0.54 N

D. 9.6 ´105 N

11.

What are the units of magnetic flux?

A. T

B. Wb

C. T ×m/A

D. N×m/C2

12.

The diagram shows a conductor between a pair of magnets. The current in the conductor flows out of the page.

In what direction will the magnetic force act on the conductor?

A. up the page

B. down the page

C. towards the left

D. towards the right

13.

The direction of a magnetic field is determined to be the direction in which

A. a positive charge would tend to move.

B. a negative charge would tend to move.

C. the north end of a compass needle would point.

D. the south end of a compass needle would point.

14.

Which diagram shows the magnetic field created near a conductor carrying current towards the right?

15.

A beam of positively and negatively charged particles enters a magnetic field as shown. Which paths illustrate the positive and negative charges leaving the magnetic field region?

16.

A solenoid has a length of 0.30 m, a diameter of 0.040 m and 500 windings. The magnetic field at its centre is 0.045 T. What is the current in the windings?

A. 2.9 A

B. 3.0 A

C. 21 A

D. 170 A

17.

The magnetic field at the centre of a solenoid of length 0.25 m is 1.2 ´10-2 T. The current in the windings is 7.5 A.

a) How many windings does the solenoid have? (4 marks)

b) If the cross-sectional area of the solenoid is 8.5 ´10-4 m2 , what is the flux through it? (3 marks)

18.

A rectangular loop is suspended by a spring scale between magnetic poles. The loop is 0.060 m wide by 0.120 m high.

As the current in the loop is varied, the readings of the spring scale and current are plotted on a graph.

a) What is the weight, in Newtons, of the loop? (1 mark)

b) What is the slope of the best fit line? (2 marks)

c) What is the magnitude of the magnetic field? (2 marks)

19.

Protons travelling at 2.2 ×105 m/s enter at right angles to a magnetic field. The field is produced by a 0.16 m long solenoid. A current of 5.3 A flows through the 820 turns of wire of the solenoid.

a) What is the magnetic field in the solenoid? (3 marks)

b) What is the radius of curvature of the proton beam in the magnetic field of the solenoid? (4 marks)

20.

An electron travelling at 7.7 ×106 m/s enters at right angles into a uniform magnetic field. Inside the field the path of the electron has a radius of 3.5 ×10-2 m.

a) What is the magnitude of the magnetic field? (4 marks)

b) If the magnetic field is produced at the centre of a solenoid by a current of 0.62 A, what is the number of turns per unit length of the solenoid? (3 marks)