Magnetic effect of current Worksheet-1

Magnetic effect of current Worksheet-1

1. Which of the following properties of a proton can change while it moves freely in a magnetic field ? (There may be more than one correct answer).

A. mass              B. speed             C. velocity          D. momentum

2. The magnetic field inside a long straight solenoid carrying current :

A. is zero

B. decreases as we move towards its end

C. increases as we move to wards its end

D. is same at all points.

3. A positively-charged particle (alpha particle) projected towards west is deflected towards north by a magnetic field. The direction of magnetic field is :

A. towards south                          B. towards east

C. downward                                 D. upward

4. A rectangular coil of copper wires is rotated in a magnetic field. The direction of the induced current changes once in each :

A. two revolutions                        B. one revolution

C. half revolution                          D. one-fourth revolution.

5. Which of the following correctly describes the magnetic field near a long straight wire ?

A. The field consists of straight lines perpendicular to the wire.

B. The field consists of straight lines parallel to the wire.

C. The field consists of radial lines originating from the wire.

D. The field consists of concentric circles centered on the wire.

6. The phenomena of electromagnetic induction is :

A. the process of charging a body,

B. the process of generating magnetic field due to a current passing through, a coil,

C. producing induced current in a coil due to relative motion between a magnet and the coil,

D. the process of rotating a coil of an electric motor.

7. The device used  for producing electric current is called a :

A. generator                                   B. galvanometer

C. ammeter                                    D. motor.

8. The essential difference between an AC generator and a DC generator is that:

A. AC generator has an electromagnet while a DC generator has permanent magnet,

B. DC generator will generate a higher voltage,

C. AC generator will generate a higher voltage,

D. AC generator has slip rings while the DC generator has a commutator.

9. At the time of short-circuit, the current in the circuit:

A. reduces substantially              B. does not change

C. increases heavily                     D. varies continuously.

10. The direction of magnetic field around a straight conductor carrying current can be determined by:

A. Right hand thumb rule

B. Fleming's right hand rule

C. Fleming's left hand rule

D. Lenz's law

11. Magnetic field is produced by the flow of current in a straight wire. This phenomenon was discovered by:

A. Faraday        B. Maxwell        C. Coulomb       D. Oersted

Answer Key:

1. C,D

2. B

Explanation: The magnetic field for a point inside a long straight solenoid carrying current is double than for a point situated at one of its ends.

3. D

Explanation: The direction of motion of proton is the direction of current (I). The direction of force (F) on the proton is towards north (as the proton is deflected towards north). Applying Fleming's left hand rule, the direction of magnetic field (B) is upward as shown by the figure.

4. C
5. D
6. C
7. A
8. D

Explanation: A DC generator is similar to an AC generator. But there is one important difference. Each end of the armature coil is connected to one half of a single split ring instead of two separate slip rings. This split ring is called a commutator.

9. C

Explanation: A low-resistance connection established by accident or intention between two points in an electric circuit is short circuit. The current tends to flow through the area of low resistance, bypassing the rest of the circuit.

10. A

Right hand rule for determining the direction of the magnetic field.

Point thumb in direction of the conventional current.

Fingers wrapped around the wire point in direction of the field.

11. D