Electrical Engineering

Difference between Node and Junction :-   1)NODE:-    A point at which two or more elements are joints together is called node.    2)JUNCTION:-      While a point   where three or more        branches  meet   together  is  called   a junction.                   In the below figure we can say that points  a,b,c,d,e  and  f  are  nodes     and point  c &  f  are  called   junction.  While point c & f itself a node. Nodes -> a,b,c,d,e,f Junctions ->c,f  By observing above node and junction we can say that,  every junction becomes a node but every node not becomes a junction. ● SHARE IT

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

   Resistor is a fundamental passive element. The  resistor  is  a circuit  component whose principle  property is  to oppose  the flow of current  through  it . Resistance  is represented by the letter "R". The symbol of the resistance is shown in below figure. Units for resistance is shown in below figure           A conductor is said to have resistance of  1  ohm , if   it  permits  one  Ampere   of current  to flow  through  it when  1 Volt is applied  across  it's  terminals.                 For conductors such as metals ,the resistance  is  very  low . This  is  due to the presence  of  free  electrons  in their atoms. For insulators  the  resistance  is very  high and for  semiconductors  the resistance lies in between that of metal and insulator.        The resistance R of a conductor depends on the following factors .  1) It is directly proportional to length of the conductor  2) It is inversely proportional to area of cross section of t

CAPACITORS :- 1. Air capacitors are generally available in the range (a) 10 to 400 pF (b) 1 to 20 pF (c) 100 to 900 pF (d) 20 to 100 pF Ans: a 2. The unit of capacitance is (a) henry (b) ohm (c) farad (d) farad/m Ans: c 3. The power dissipated in a pure capacitor is (a) zero (b) proportional to value of capacitance  (c) proportional to applied voltage (d) both (b) and (c) above Ans: a 4. Which of the following materials has the highest value of dielectric constant? (a) Glass (b) Vacuum (c) Ceramics (d) Oil Ans: c 5. In a capacitor the electric charge is stored in (a) metal plates (b) dielectric (c) both (a) and (b) (d) none of the above Ans: b