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  • (a) For the combination of resistors shown in the following figure, find the equivalent resistance between M & N. <img src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAPoAAACuCAYAAAAf8xDcAAAW7ElEQVR4nO2dv5ab1hPHufgF4sI4hdBJ/dMLLNtY+w6C

(a) For the combination of resistors shown in the following figure, find the equivalent resistance between M & N.

(b) State Joule’s law of heating.
(c) Why we need a 5 A fuse for an electric iron which consumes 1 kW power at 220 V ?
(d) Why is it impracticable to connect an electric bulb and an electric heater in series ?

 

 
 
 
 
 

Answers (1)

(a) R3 and R4 are in parallel combination.

∴ Rparallel  is given by

1 / Rp = 1/ R3 + 1/ R4

1/Rp = R4+ R3/ R3R4

Rp = R3R4/ R4+ R3

Now, R1 R2 and Rp are in series.

∴ Req = R1 + R2 + Rp

= R1 + R2 + R3R4/ R4+ R3

 

b) Jouls Law of Heating refers to-  

The heat produced in a resistor is directly proportional to

1. Square of current for a given resistance.

2. The resistance for a given current and

3. The time for which the current flows through the resistor

(c) P = V I or I = P/ V

I = 1000 watt/ 220 volt = 4.54 A

Since 4.54 ampere current flows in the circuit , a 5 A fuse must be used.

(d) It is impracticable to connect an electric bulb and an electric heater in series because Electric bulb & electric heater will not get currents and voltages as per their requirement.

Posted by

Safeer PP

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