Question

1.   AN ELECTRIC HEATER DRAWS A CURRENT OF 5A WHEN IT IS CONNECTED TO 110V. WHAT CURRENT WILL THE HEATER DRAW WHEN IT IS CONNECTED TO 220V?

2.    EXPLAIN WHY METALS OF LOW RESISTIVITY ARE USED IN TRANSMISSION OF ELECTRICITY?

Answer 1

1. it will draw 10 A as R=22 ohm

2. to avoid loss of energy in the form of heat

Answer 2

1. Current(I) = 5 Amperes
P.D(V) = 110 V
So now we can find resistance by ohm's law.
V = I * R                                    (OHM'S LAW)
110V = 5A * R
Therefore, R= 110/5 Ohms = 22 Ohms                ..........(i)
Here we have found that Resistance of heater is 22 ohms which remains constant if voltage or current vary.

So in the second case when the voltage is 220 V. Then we can find current by ohm's law again.
V = I * R
220V = I * 22                                  {R= 22 ohms from equation (i)}
I = 220V/22Ohms = 10 A
SO THE ANSWER WILL BE 10 A

2. Metal of low resistivity is used in transmission because it offers low resistance. If their will be low resistance then their will be less heat energy dissipated/consumed as H(Heat energy) is directly proportional R as per as Joule's law of heating(NOTE- If you are in class 10 of CBSE board then you will learn about this in electricity chapter).