Magnetic effect of current Worksheet-4

Magnetic effect of current Worksheet-4

1. Why does a compass needle get deflected when brought near a bar magnet ?

2. Why don't two magnetic field lines intersect each other ?

3. Consider a circular loop of wire lying in the plane of the table. Let the current pass through the loop clockwise. Apply the right hand rule to find out the direction, of magnetic field inside and outside the loop.

4. The magnetic field in a given region is uniform. Draw a diagram to represent it

5. In the given figure how do you think the displacement of rod AB will be affected if (i) current in the rod AB is increased, (ii) a stronger horse-shoe magnet is used ; and (iii) length of the rod AB is increased ?

6. Explain different ways to induce current in a coil.

7. What is the role of the split-ring in an electric motor ?

8. State the principle of an electric generator.

9. Name some sources of direct current .

10. Which sources produce alternating current ?

Answer:

1. A compass needle gets deflected due to the forces acting on its poles due to the magnetic field of the bar magnet.

2. The direction of magnetic field (B) at any point is obtained by drawing a tangent to the magnetic field line at that point, in case, two magnetic field lines intersect each other at the point P as shown in the figure, magnetic field at P will have two directions, shown by two arrows, one drawn to each magnetic field line at P, which is not possible.

3. The magnetic field inside and outside the loop, found by applying right hand thumb rule is as shown in the figure. These dotted magnetic field lines are perpendicular to the plane of the paper. The front face of the loop is the south-pole and back face, i.e., the face touching the table is a north-pole.

4. Parallel and equidistant magnetic field lines for representing a uniform magnetic field in a region are shown here.

5. Force (F) acting on a conductor of length (i) carrying current (I) placed in a magnetic field (B) is given by

          F = I/B

(i) If the current (I) in the rod AB is increased, F also increases.

(ii) When a stronger horse-shoe magnet is used, B increases. On account of this F also increases. (l) If the length (I) of the rod is increased, F also increases.

6. To induce current in a coil, the magnetic flux linked with it is to be changed. This can be done if:

(a) there is a relative motion between the coil and the magnet.

(b) there is a relative motion between the coil and the conductor carrying current,

(c) there is a change in the current in a conductor placed near the coil.

7. With the help of split-ring commutator, the direction of the current through the coil gets reversed after every half rotation of the coil. Thus, the direction of rotating couple remains unchanged and the coil continues to rotate in the same direction.

8. Whenever in a closed circuit, the magnetic field lines change, an induced current is produced.

9. A battery, a DC generator, a solar cell.

10. An AC generator, an oscillator that converts DC into AC.