Electrical Engineering MCQ Multiple Choice Questions and Answers 16-30

Multiple Choice Questions of Electric Current and Ohm's Law (16-30):

16.Conductance is expressed in terms of

(A) ohm / m

(B) m / ohm

(C) mho / m

(D) mho.


17. Which of the following could be the value of resistivity of copper?

(A) 1.7 x 10-8 ohm-cm

(B). 1.7 x 10-6 ohm-cm

(C). 1.6 x 10-5 ohm-cm

(D). 1.7 x 10-4 ohm-cm


18. 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 wire is made d/3, then drift velocity becomes

(A) 9 vd

(B) vd / 9

(C)vd /3

(D)vd.


19.Two resistances R1 and R2 give combined resistance of 4.5 ohms when in series and 1 ohm when in parallel. The resistances are

(A)3 ohms and 6 ohms

(B)3 ohms and 9 ohms

(C)1.5 ohms and 3 ohms

(D)1.5 ohms and 0.5 ohms.



20. We have three resistances of values 2 Ω, 3 Ω and 6 Ω. Which of the following combination will give an effective resistance of 4 Ω?

(A) All the three resistances in parallel

(B) 2 Ω resistance in series with parallel combination of 3 Ω and 6 Ω resistance

(C) 3 Ω resistance in series with parallel combination of 2 Ω and 6 Ω resistance

(D) 6 Ω resistance in series with parallel combination of 2 Ω and 3 Ω resistance.


21. Three equal resistors connected in series across a source of emf together dissipate 10 watts of power. What would be the power dissipated in the same resistors when they are connected in parallel across the same source of emf?

(A) 10 watts

(B) 30 watts

(C) 90 watts

(D) 270 watts.


22.Current I in the figure is




(A)1.5A

(B)0.5A

(C)3.5A

(D)2.5A


23.Four identical resistors are first connected in parallel and then in series. The resultant resistance of the first combination to the second will be

(A) 1 / 16 times

(B) 1 / 4 times

(C) 4 times

(D) 16 times.

24.Twelve wires of same length and same cross-section are connected in the form of a cube as shown in figure below. If the resistance of each wire is R, then the effective resistance between P and Q will be


(A)R

(B) 5 / 6 R

(C) 3 / 4 R

(D) 4 / 3 R.


25. When P = Power, V = Voltage, I = Current, R = Resistance and G = Conductance, which of the following relation is incorrect?

(A) V = √ (PR)

(B). P= V2G

(C) G= P / I2

(D) I =√ (P / R)


26.The unit of electrical conductivity is

(A) mho / metre

(B) mho / sq. m

(C) ohm / metre

(D) ohm / sq. m.


27.Which of the following bulbs will have the least resistance ?

(A) 220 V, 60 W

(B) 220 V, 100 W

(C) 115 V, 60 W

(D) 115 V, 100 W.


28.The ratio of the resistance of a 100 W, 220 V lamp to that of a 100 W, 110 V lamp will be nearly

(A) 4

(B)2

(C) 1 / 2

(D) 1 / 4


29.The resistance of a 100 W, 200 V lamp is

(A) 100 ohm

(B) 200 ohm

(C) 400 ohm

(D) 1600 ohm.


30.Two 1 kilo ohm, 1/2 W resistors are connected in series. Their combined resistance value and wattage will be

(A) 2 kΩ, 1/2 W

(B) 2 kΩ, 1 W

(C) 2 kΩ, 2 W

(D) l kΩ, 1/2 W.



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