Question

Derive an expression for the equivalent resistance of three resistors R, R. and R, connected in
senes
Fuse of 3 A, 5 A and 10 A are available. Calculate and select the fuse for operating an electric
ran of 1 W power at 220 V line​

Answer 1

Answer:

We know that in series current is same and output voltage is sum of voltages whose resistance to be found

V=V'+V"+V"'

IR=IR'+IR"+IR"'

I is same

therefore

R=R'+R"+R"'

=1kW=1000W

V=220V

From this, we can find the Current at which the Electric Iron is supposed to operate.

2nd Q

1KW=1000W

V=220V

From this, we can find the Current

P=VI

⟹I=V/P

⟹I=1000/220

I≈4.545A

If the current is much more than 4.5 amperes, the electric iron can get damaged.

We cannot use a fuse of 3 A. It would prevent the iron from operating at its desired capacity.

We also cannot use a 10 A fuse. It wouldn't provide protection if the current becomes, say, 7 A or 8 A.

Thus, We must use the 5 A fuse. It will protect the iron from voltage and current overloading.