Choose the correct alternatives and rewrite the complete sentences
*1. The device used for producing current is called a ..................... .
(a) voltmeter (b) ammeter (c) galvanometer (d) generator
*2. At the time of short circuit, the current in the circuit ..................... .
(a) increases (b) decreases (c) remains (d) increases in steps
*3. The direction of the magnetic field around a straight conductor carrying current is given by ..................... .
(a) right hand rule (b) Fleming’s left hand rule
(c) Fleming’s right hand rule (d) non of these
4. The relation between electricity and magnetism was first established by ..................... .
(a) Ohm (b) Ampere (c) Oersted (d) Moseley
5. The region around magnet is called as .............. .
(a) magnetic Area (b) magnetic field (c) magnetic loop (d) magnetism
6. Oersted proved that when current passes through a conducting wire it produces ..................... .
(a) charge (b) current (c) magnetic field (d) potential difference
7. The relative strength of magnetic field is shown by ..................... .
(a) degree of closeness of field lines (b) optical lines
(c) current flowing (d) potential difference
8. The magnetic field produced at centre of circular wire is inversely
proportional to ..................... .
(a) magnitude of current (b) radius of circular wire
(c) resistance of wire (d) time for which current is passed
9. Solenoid has properties similar to ..................... .
(a) magnet (b) resistance (c) electric motor (d) optical instruments
10. The magnetic field in solenoid depends on ..................... .
(a) current and number of turns per unit length
(b) current only
(c) Number of turn per unit length
(d) material
11. In India, the frequency of A.C is ..................... cycles per second.
(a) 50 (b) 100 (c) 60 (d) none
12. The magnetic field produced at centre of circular wire is directly proportional to ..................... .
(a) magnitude of current passing through it
(b) radius of the loop
(c) resistance of wire
(d) time for which the current passes through it.
13. The non-oscillating current is called as ..................... .
(a) A.C. (b) D.C. (c) electric current (d) non-oscillating current
14. The ..................... at any point on the magnetic lines of force gives the direction of the magnetic field at that point.
(a) tangent (b) circle (c) radius (d) chord
15. ..................... is an alloy of iron, nickel, aluminium and titanium.
(a) Nipermag (b) Nichrome (c) Alnico (d) Tin
16. ..................... is aluminium-nickel-cobalt alloy.
(a) Alnico (b) Tin (c) Nichrome (d) Nipermag
17. If a conductor is moving inside a magnetic field or magnetic field is changing around a fixed conductor ..................... is generated.
(a) electric current (b) heat (c) sparks (d) light
18. The process, by which a changing magnetic field in a conductor induces a current in another conductor, is called ..................... .
(a) electromagnetic induction (b) potential difference (c) electrostatics (d) sparks
19. If a live wire and a neutral wire comes in direct contact or touch each other, ..................... takes place.
(a) short circuiting (b) magnetic effect (c) heating (d) electro-magnetism
20. ..................... means the flow of large amount of current in the circuit beyond the permissible value of current.
(a) Overloading (b) Drip (c) Sparkling (d) Resistance
21. French scientist ..................... suggested that the magnet must also exert an equal and opposite force on the current carrying conductor.
(a) joule (b) newton (c) ampere (d) fleming
22. ..................... reverses the direction of current in the armature coil of electric motor.
(a) Brushes (b) Armature coil (c) Magnet (d) Commutator
23. The direction of induced current in an AC generator changes once in each ..................... .
(a) two revolutions (b) one revolution (c) half revolution (d) one fourth revolution
24. A ..................... is used to detect the presence of current in a circuit.
(a) voltmeter (b) variable resistance (c) galvanometer (d) Tap key
25. Electro-magnetic induction was first studied by ..................... .
(a) Ampere (b) Faraday (c) Oersted (d) Joule
A. Answers.
1. Generator
2. Increases
3. Right hand rule
4. Oersted
5. Magnetic field
6. Magnetic field
7. Degree of closeness of field lines
8. Radius of circular wire
9. Magnet
10. Current and number of turns per unit length
11. 50
12. Magnitude of current passing
13. D.C.
14. Tangent
15. Nipermag
16. Alnico
17. Electric current
18. Electromagnetic induction
19. Short circuiting
20. Overloading
21. Ampere
22. Commutator
23. Half revolution
24. Galvanometer
25. Faraday 