Question 1 If the current in a wire is flowing in the vertically downward direction and a magnetic field is applied from west to east, what is the direction of force on the wire? Solution
By fleming left hand rule, the direction of force will be towards south
Question 2 When do we apply Flemings (i) Left hand (ii) Right hand rule.> Solution
Flemings Left hand rule is used to find the force experience by the current carrying conductor in Magnetic Field
Flemings Right hand rule is used to find the direction of induced current of moving conductor in magnetic field
Question 3 How much force is exerted by a magnetic field on a stationary charge? Solution
Question 4 A positive charge is moving vertically upwards, when it enters a region of magnetic field directed toward north, what is the direction of force on the charge? Solution
Two marks questions
Question 5 Two circular coils A and B are placed closed to each other. If the current in the coil A is changed, will some current be induced in the coil B? Give reason. Solution
When the current in coil A is changed, the magnetic field associated with it also changes. As a result, the magnetic field around coil B also changes. This change in magnetic field lines around coil B induces an electric current in it. This principle is called electromagnetic induction.
Question 6 State the principle of an electric generator. Question 7 What is the function of a split ring in an electric motor? Question 8 (a) Why do we connect earth wire in a house? Give two reasons.
(b) What type of current is used in house hold supply and what type of current is given by a cell? Solution
a) Earth wire are used to prevent electric shock to us
b) Alternating Current(AC) is used in house hold supply and Direct Current(DC) is given by cell
Question 9 To which wire do you connect fuse wire in a house hold circuit? Write name of one source of AC current and one source of DC current. Solution
Fuse wire is connected to the Live wire.House hold supply is AC current and Electric cell provides DC current
Three marks questions
Question 10 (a) Define the term current rating of an electric fuse?
(b) Name the material used to make electric fuse?
(c) Name two safety measure commonly used in electric circuit and appliances? Solution
a) Electric Fuse current rating defines the maximum value of safe current allowed to flow through fuse with out melting it
b) Tin-lead alloy is general used to make fuse wire
c) Electric Fuse and Earthing
Question 11 Draw a labelled diagram of an electric motor. Explain its principle and working. Question 12 A coil made of insulated copper wire is connected to a galvanometer. What will happen to the deflection of the galvanometer if bar magnet is pushed into the coil and then pulled out of it. Give reason for your answer and the phenomenon involved. Solution
When bar magnet is pushed into the coil, a current will be induced in the coil. The current in the coil will let the galvanometer show a deflection.
When bar magnet is pulled out of coil it will again induce a current in the coil but this time the current will be induced opposite to the previous direction. The galvanometer will deflect in opposite direction.
When the bar magnet is pushed or pulled ,the magnetic field associated with the coil is changed And changing magnetic field leads to an induced current in the conductor. So current flows in the coil and deflection is shown in galvanometer
The phenomenon is known as electromagnetic induction.