Magnetic Effects of Electric Current Test - 9

Materials used to make permanent magnets are Alnico an alloy of aluminium, nickle , cobalt . Neodymium magnets are widely used for computer hard disks. these magnets are the strongest.

According to clock rule if we look at the face of the coil which carries current in the clock wise direction then the face is called as south pole looking from the other side of coil we find that anti clock wise current flows that is called as north pole.

It leads to the burning of the fuse wire because of the excessive flow of current , the temperature of the wire goes beyond the melting point of the fuse wire and hence it is melts by burning . So, (A) and (B) are correct reason.

If we Place a straight current carrying wire (the direction of the flow current is from north to south) such that the wire is placed below a compass needle such that the wire is parallel to the compass needle, the north pole of the compass needle deflects towards the west.

(A) To keep the torque on a DC motor from reversing every time the coil moves through the plane perpendicular to the magnetic field, a split-ring device called a commutator is used to reverse the current at that point..
(B) The induced current produced in conductor is not move direct in nature.
So, statement (A) is true and (B) is false.

An electric generator converts mechanical energy into electrical energy, while a motor does the opposite - it converts electrical energy into mechanical energy.

The direction of induced current in a straight conductor is given by Fleming’s right hand rule.
It states that if we stretch the thumb, forefinger and the middle finger of right hand at right angles to one another in such a way that the forefinger points in the direction of magnetic field.
Then, thumb gives the direction of motion of conductor (force), forefinger indicates direction of magnetic field and the middle finger points the direction of induced current.

A. The magnetic field of a straight conductor is concentric around the conductor, so the fieldlines don't seem to start or end anywhere, so there are no poles.

B. When two magnets are placed with their like poles facing each other, the lines of force are in opposite directions and hence like poles repel each other. 

The direction of force which acts on the current-carrying conductor placed in a magnetic field is given by Fleming’s left hand rule. It states that if the forefinger, thumb and middle finger of left hand are stretched mutually perpendicular and the forefinger points along the direction of external magnetic field, middle finger indicates the direction of current, then thumb points along the direction of force acting on the conductor.

According to Faradays law, as the loop is a closed loop, hence there will be a rise in induced current due to that the galvanometer shows a deflection,the deflection due to the ON and OFF will be opposite as when the battery is on the current will be high.