Magnetic Effect of Electric Current--Vasu Classes


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Magnetic Effect of Electric Current--Vasu Classes

1. A domestic lighting circuit has a fuse wire of 10Amp. If the mains supply is 220V, the number of bulbs 100W can be safely used will be....

a) 10
b) 20
c) 22
d) 40

2. How much energy is consumed by an electric geyser of 2KW in 2hrs

a) 1unit
b) 3units
c) 8units
d) 4units

3. A charged body at rest produces

a) Electric field
b) Gravitational field
c) Magnetic field
d) None

4. Magnetic field does not interact with

a) Electric charge at rest
b) Electric charge in motion
c) Magnet in rest
d) Magnet in motion

5. Current carrying coductor placed in a magnetic field experiences a force , the device based on this principle is

a) Electric generator
b) Electric motor
c) Transformer
d) All of the above

6. The polarity of electromagnet can be reversed by

a) Changing number of turns
b) By changing core material
c) By changing direction of current
d) can not be changed

7. The phenomenon of electromagnetic induction is

a) process of charging a body
b) process of generatig magnetic field due to a current passing through a coil
c) producing induced current in a coil due to relative motion between a magnet and the coil.
d) the process of rotating the coil of an electric motor

8. The device used to produce electric current is called...

a) generator
b) galvanometer
c) ammeter
d) motor

9. The essentila difference between an AC generator and DC generator is that....

a) first one has electromagnet and second one has permanent magnet
b) DC generator produces high voltage
c) AC generator produces higher voltage.
d) AC generator has slip rings while DC generaor has commutator

10. At the time of short circuit the current in the circuit..

a) reduces substantially
b) does not change
c) increases heavily
d) vary continuously

11. SI unit if magnetic field intensity is

a) Gauss
b) Torr
c) Tesla
d) Newton

12. The force exerted on a conductor of length 50cm carrying a current a current of 4Amp when placed in a Magnetic field 6 X 10^-7 tesla

a) 1.2 x 10^-7 N
b) 2.4 X 10^7 N
c) 4.8 X 10^9 N
d) None

13. Permanent magnets are not used in

a) Loudspeakers
b) Galvanometer
c) Ammeter
d) Call bells

14. Shape of magnetic field lines caused by a straight current carrying condcuctor are

a) Curved
b) Concentric circles
c) straight lines
d) Uneven curved lines

15. Function of slip rings in a DC motor is

a) To change the direction of current in the coil
b) to stop motor suddenly
c) to produce DC
d) allow the motor to rotate in one direction

16. If air gap between the poles of an electromagnet is increased

a) Magnetic field remains same
b) magnetic field increases
c) magnetic field decreases
d) to increase current

17. Which rule is used to find the direction of magnetic field at the centre of a current carrrying loop

a) Right hand thumb rule
b) Left hand riule
c) Right hand rule
d) Raght hand palm rule

18. A beam of alpha particles is moving from east to west when enters in a magnetic field, bends towards left what is the direction of magntic field

a) downward
b) Upward
c) Into the page
d) None

19. Which wire is thickest

a) Live wire
b) earth wire
c) Neutral wire
d) None

20. In India electricity is supplied at

a) 220V-50Hz
b) 110V-50Hz
c) 220V-100Hz
d) 100V-50Hz

21. Switches are connected to

a) Live wire
b) Neutral wire
c) Earth wire
d) any one

22. When North pole of a bar magnet is brought towards a metallic coil , the induced current flows such that the side of the coil towards magnet develops

a) North pole
b) South pole
c) polarity depends upon speed of magnet
d) None

23. The use of fuse is

a) to control the voltage
b) to supply hogh current in case of short circuit
c) to supply high current in case of overloading
d) to stop supply of current in case of overloading and short circuit

24. When a coil is moved towards a stationary magnet , the induced emf does not depend upon

a) number of turns in the coil
b) strength of magnet
c) speed at which the coil is moved
d) resistance of the coil

25. A rectangular coil of copper is rotated in a magnetic field. The direction of the induced current changes once in each

a) two revolutions
b) one revolution
c) half revolution
d) one fourth revolution

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