Electrical Engineering

1. A conductor is a substance which has (A) There is no free electrons. (B) Small number of free electrons. (C) Large number of free electrons. (D) none of the above. 2)Why voltage is applied to the conductor ? (A) For moving free electrons in the conductor. (B) for producing heat in the conductor. (C) for removing heat in the conductor. (D) for blocking the free electrons. 3.Which of the following are the good conductors (A) gold (B) silver (C) copper (D)all the above. 4.An insulator (A) a poor conductor of electricity. (B) no free electrons in it. (C) to block the flow of electrons. (D) all the above. 5.One Ampere is equal to (A) 1.602×10^19 electrons/second (B) 6.242×10^-18 electrons/second (C) 6.242×10^18 electrons/second (D) 1.602×10^-19 electrons/second 6.An Electrical charge is equal to (A) 6.242×10^19 (B) 1.602×10^-19 (C) 6.242×10^-19 (D) 1.602×10^19

Q. In direct current , the phase angle between voltage and current is (A) 90° (B) 0° Explanation :-  The power in the DC is                  P = V × I Now we have to know about the phase angle between voltage and current , then the the power in the AC is P = V × I cos ( Φ)  When  Φ= 90° :- i .e.,        P = V × I (cos 90°)                P = V × I ( 0)                P = 0 Watts When  Φ= 0° :- i.e.,     P = V × I (cos 0°)            P = V × I (1)            P  = VI So  , the phase angle between voltage and current is 0 °.

Q. What is the current through the 8 ohms resistance connected across terminals M and N in the circuit as shown in below figure. A)0.34 A from M to N. B)0.29 A from M to N. C)0.29 A from N to M. D)0.34 A from N to M. Solution :- We have to redraw the circuit as shown in below figure  Apply KCL at node Vo,we get  ((Vo+8)/12)+(Vo/8)+((Vo+2)/8)=0 (Vo/12)+(Vo/8)+(Vo/8)= - [(8÷12)+(2÷8)] Vo[(1/12)+(1/8)+(1/8)]= - 0.916 => Vo(0.333)= - 0.916 => Vo =  - (0.916÷0.333) =>  Vo = -(2.75). Volts Vo is the voltage across M and N , Current I at the 8 ohms resistor is, I = Vo/ Resistance at 8 ohms I=(-2.75)÷8 I= - 0.34 Amperes The current between M and N is - 0.34  Amperes  Now we have to interchange the terminals we can get positive current . i.e., the current 0.34 A current flows from terminal N to terminal M . Ans is option D. 👍👍 All The Best 👍👍 Share it