Question

1. The coils have the direction of the wrapped turns indicated on the top: if you look down from above the direction is clockwise. Using the right hand rule, what is the direction of the area vector for these loops of wire?

   		up
   		down
   		clockwise
   		counter-clockwise

Question 3

1. If the magnet is allowed to fall with its north pole down, that is, entering the coil first, in what direction does the magnetic field point?

   		up
   		clockwise (when viewed from above)
   		counter-clockwise (when viewed from above)
   		down

Question 4

1. Given the two directions in your answers to the previous two questions, what is the sign of the magnetic flux?

   		positive
   		negative
   		zero

Question 5

1. As the magnet enters, what will be the sign of the induced emf?

   		negative
   		zero
   		positive

Answer 1

Activity 1

• Take a straight thick copper wire and place it between the points X and Y in an electric circuit, as shown in Fig. 1.
• Place a small compass near to this copper wire. See the position of its needle.
• Pass the current through the circuit by inserting the key into the plug.
• Observe the change in the position of the compass needle.

Fig. 1 Compass needle is deflected on passing an electric current through a metallic conductor

We see that the needle is deflected. What does it mean? It means that the electric current through the copper wire has produced a magnetic effect. Thus we can say that electricity and magnetism are linked to each other. Then, what about the reverse possibility of an electric effect of moving magnets? In this Chapter we will study magnetic fields and such electromagnetic effects. We shall also study about electromagnets and electric motors which involve the magnetic effect of electric current, and electric generators which involve the electric effect of moving magnets.