Basic Electrical Science (Practice test)

1) Resistivity of a wire depends on
A. material
B. length
C. cross section area
D. all of above
                                   
2) When n numbers resistances of each value r are connected in parallel, then the resultant resistance is x. When these n resistances are connected in series, total resistance is
A. nx.
B. n2x.
C. x/n.
D. rnx.

3) Resistance of a wire is r ohms. The wire is stretched to double its length, then its resistance will be
A.        r/2
B.         4r
C.        2r
D.        r/4
                                   
4) Kirchhoff's second law is based on law of conservation of
A.        charge
B.         energy
C.        momentum
D.        mass
                                   
5) One coulomb of electrical charge is contributed by how many electrons ?
A.        0.625 X 1019.
B.         1.6 X 1019.
C.        1019.
D.        1.6 X 1012.
                                   
6) Tow bulbs marked 200 watts - 250 V, and 100 watts - 250 V are joined in series to 250 V supply. The power consumed by the circuit is
A.        33 watt
B.         200 watt
C.        300 watt
D.        67 watt.
                                   
7) Ampere second is the unit of
A.        conductance
B.         power
C.        energy
D.        charge
                                   
8) Which of the following is not the unit of electrical power
A.        volt/ampere
B.         volt ampere
C.        watt
D.        joule/second
                                   
9) One kilowatt hour is same as
A.        36 X 105 watt
B.         36 X 105 ergs
C.        36 X 105 joules
D.        36 X 105 BTU
                                   
10) An electric current of 6 A is same as
A.        6 joule/second
B.         6 Coulomb/second.
C.        6 watt/second
D.        none of the above.
                                   
11) A circuit contains two un equal resistor in parallel
A.        voltage drops across both are same
B.         currents in both are same
C.        heat losses in both are same
D.        voltage drops are according to their resistive value
                                   
12) Conductance of any conductor is expressed as

A.        ampere/watt
B.         mho
C.        volt2/watt
D.        watt/ampere2
                                   
13) A copper wire of length l and diameter d has potential difference V applied at its two ends. The drift velocity is vd. If the diameter of the wire is made d/2, then the drift velocity becomes
A.        vd.
B.         4vd.
C.        vd/4.
D.        vd/2.
                                   
14) Two resistances R1 and R2 give combined resistances 4.5Ω and 1Ω when they are connected in series and parallel respectively. What would be the values of these resistances ?
A.        3Ω and 6Ω
B.         1.5Ω and 3Ω
C.        3Ω and 9Ω
D.        6Ω and 9Ω
                                   
15) Which of the following may be value of resistivity of copper
A.        1.7 X 10-6
B.         1.7 X 10-5
C.        1.7 X 10-4
D.        1.7 X 10-3
                                   
16) Mass of a proton is how many times greater than mass of an electron
A.        184000
B.         18400
C.        1840
D.        184

Answers
1. a      2. b      3. b      4. b      5. a      6. d      7. d      8. a      9. c      10. b
11. a    12. b    13. a    14. b    15. a    16. c

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