Advertisements
Advertisements
Question
State three factors which govern the speed of rotation of an electric motor.
Advertisements
Solution
(i) The strength of current in the coil,
(ii) The number of turns in the coil,
(iii) The strength of the magnetic field.
APPEARS IN
RELATED QUESTIONS
Name and state the rule by which polarity at the ends of a current carrying solenoid is determined.
State three uses of an electromagnet?
Name the material of core in (a) an electric bell, (b) electromagnet, (c) a d.c. motor, (d) an a.c. generator and (e) a transformer.
State the two properties of the magnetic lines of force around a circular coil.
A straight wire is held vertical and current is passed in it in the upward direction. A compass needle is kept near the wire in north of it. How is the needle deflected? What is the change in the deflection of the needle if the current in wire is reversed?
How does a magnetic field set up by a solenoid change when strength of current in the solenoid is decreased?
State the condition when an electric charge can give rise to a magnetic field.
The primary windings of a step-up transformer are usually made of thicker wire than the secondary. Explain.
Point out three differences between an electromagnet and a bar (or permanent) magnet.
(i) A straight wire conductor passes vertically through a piece of cardboard sprinkled with iron filings. Copy the diagram and show the setting of iron filings when a current is passed through the wire in the upward direction and the cardboard is tapped gently. Draw arrows to represent the direction of the magnetic field lines.

(ii) Name the law which helped you to find the direction of the magnetic field lines.
