Magnetic Effects of Electric Current Question

Magnetic Effects of Electric Current Question 

Multiple Choice Questions

1. Choose the incorrect statement from the following regarding magnetic lines of field

(a) The direction of the magnetic field at a point is taken to be the direction in which the north pole of a magnetic compass needle points

(b) Magnetic field lines are closed curves

(c) If magnetic field lines are parallel and equidistant, they represent zero-field strength

(d) Relative strength of the magnetic field is shown by the degree of closeness of the field lines

2. If the key in the arrangement is taken out (the circuit is made open) and magnetic field lines are drawn over the horizontal plane ABCD, the lines are

(a) concentric circles

(b) elliptical in shape

(c) straight lines parallel to each other

(d) concentric circles near the point O but of elliptical shapes as we go away from it.

Ans: (c)

3. A constant current flows in a horizontal wire in the plane of the paper from east to west as shown in Figure. The direction of the magnetic field at a point will be North to South

(a) directly above the wire

(b) directly below the wire

(c) at a point located in the plane of the paper, on the north side of the wire

(d) at a point located in the plane of the paper, on the south side of the wire

Ans: (b)

Questions 

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

2.  Why does a magnetic compass needle pointing North and South in the absence of a nearby magnet get deflected when a bar magnet or a current-carrying loop is brought near it. Describe some salient features of magnetic lines of field concept.

3. A magnetic compass needle is placed in the plane of paper near point A as shown in Figure.

In which plane should a straight current-carrying conductor be placed so that it passes through A and there is no change in the deflection of the compass? Under what condition is the deflection maximum and why?

4. AB is a current-carrying conductor in the plane of the paper as shown in Figure.

What are the directions of magnetic fields produced by it at points P and Q? Given `r_1 > r_2`, where will the strength of the magnetic field be larger?

5. A circuit contains a battery, a variable resistor and a solenoid. The figure below shows the magnetic field pattern produced by the current in the solenoid.

a. State how the magnetic field pattern indicates regions where the magnetic field is stronger.

b. What happens to the magnetic field when the current in the circuit is reversed?

Ans: 

a. Relative closeness of field lines indicates the strength of the magnetic field. Since field lines are crowded around the ends of the solenoid, hence these are the regions of strongest magnetism.

b. The direction of the field will also be reversed.

6. A student makes an arrangement to study electromagnetic induction, as shown.

She changes the arrangement in four different ways.

In which trial the galvanometer would remain undeflected?