Electric current - part (1)

21. A fuse is used in main electric supply as a safety device which one of the following statement about the fuse is correct ? [I.A.S. (PRE) 1998]

(a) it is connected with the parallel with the main switch.
(b) it is made only from silver alloy.
(c) it must have a low melting point.
(d) it must have very high resistance.

Correct Answer: (c) it must have a low melting point.

Solution:An electric fuse is a safety device is used to prevent the damage to an electric circuit when the excessive current the follows through it. the electric fuse works on the principle of the heating effect of the electric current.

As the current flows beyond the limit of the wire in the electric fuse melts and break off thus then fuse have to said is blown off. The circuit is broken and the current stop flowing through circuit .Thus fuse prevents fires.

22. A fuse wire is a characterised by : [U.P.P.C.S.(pre) 1993]

(a) low resistance and high melting point.
(b) low resistance and low melting point.
(c) high resistance and low melting point.
(d) high resistance and high melting point.

Correct Answer: (c) high resistance and low melting point.

Solution:Fuse of a piece of wire with the high resistance and very low melting point when the high current flow through the circuit it gets heated and melts.

23. Fuse wire used for safety of household have ; [R.A.S/R.T.S (PRE) 1999]

Correct Answer: (a) low melting point.

Solution:Fuse of a piece of wire with the high resistance and very low melting point when the high current flow through the circuit it gets heated and melts.

24. The filament of a halogen lamp is an alloy of - [R.A.S/R.T.S (PRE) 1999]

(a) tungsten and iodine.
(b) tungsten and bromine.
(c) tungsten and sodium.
(d) molybdenum and sodium.

Correct Answer: (c) tungsten and sodium.

Solution:The filament of a halogen lamp is an alloy of tungsten and sodium due to the presence of sodium in filament it produce yellow light.

25. Assertion (A) : The temperature of a metal wire rises when the electric current is passed through it. [I.A.S. (PRE) 1998]

Reason (R) : collision of metals atoms with each other release heat energy.
code :

(a) both (A) and (R) are correct and (R) is the correct explanation of (A).
(b) both (A) and (R) are correct and (R) is not the correct explanation of (A).
(c) (A) is the correct but (R) is wrong.
(d) (A) is the wrong but (R) is correct.

Correct Answer: (c) (A) is the correct but (R) is wrong.

Solution:When electric current passes through the conducting wire moving electrons continuously collide with the atoms of the conductor in the process they transfer their energy to the atoms of the conductor and therefore temperature of the conductor increase thus the assertion (A) is correct but the reason (R) is false.

26. Domestic electric wiring is basically a : [I.A.S. (PRE) 1996]

(a) series connection.
(b) parallel connection.
(c) combination of series and parallel connection.
(d) series connection within each room and parallel connection eleswhere.

Correct Answer: (b) parallel connection.

Solution:Domestic electrical wiring is basically a parallel connection. in parallel circuit each branch receives equal potential difference in a parallel connection if one of the bulbs is removed from the circuit ,if one of the branches in the circuit is broken electric current will still flow in other branches and other bulbs will continue to glow.

27. A wire with black insulation during electric supply is - [Chhattisgarh P.C.S.(PRE) 2014]

Correct Answer: (c) neutral wire

Solution:The electric power line reaches our home through three wire namely a live wire, neutral wire and earth wire to avoid confusion we follow a colour code for insulting these a wire the red wire is a live wire and the black wire is neutral the earth wire is given green plastic insulation. .

28. What is the order of magnitude of electric resistance of the human body (dry) ? [I.A.S. (PRE) 2005]

(a) 10² ohm
(b) 10⁴ ohm
(c) 10⁶ ohm
(d) 10⁶ohm

Correct Answer: (b) 10⁴ ohm

Solution:The order of magnitude of electric resistance of the human body is generally in the range of 10⁴(10000) ohms and it may be as high as 10⁵ (100000) ohms or more wet or broken skin the body resistance to 1000 ohms or less.

29. Full form of C.F.L is - [U.P.P.C.S.(MAINS) 2015]

(a) compact fluorescent lamp.
(b) centrally fixed lamp.
(c) chemical fluorescent lamp.
(d) condensed fluorescent lamp.

Correct Answer: (a) compact fluorescent lamp.

Solution:C.F.L is short form of compact fluorescent lamp. CFL uses less energy than the traditional light bulb (about 75 percent less ).

30. Light emitting diode (LED) work on the principle of : [Jharkhand P.C.S. (PRE) 2021]

(a) laser
(b) thermionic emission
(c) photoelectric code
(d) electroluminiescence

Correct Answer: (d) electroluminiescence

Solution:Light emitting diode (LED) work on the principle of electroluminiescence . Electroluminiescence is an optical and electrical phenomenon in which material emits light in response to the passage of an electric current or to strong electric field.

Electric current – part (1)