Question

What is a)the highest and b) lowest total resistance that can be secured by the combination of 2 coils of resistance 4 ohm and 8 ohm

Answer 1

TOPIC :- RESISTANCES

SUB-TOPIC:- Equivalent resistance in case when resistances are arranged in series or parallel combination.

• Concept used :- In series combination, equivalent resistance is the sum of the resistance and it is greater than individual resistance.

• In parallel combination, equivalent resistance is half the harmonic mean of two resistances and is lesser than the two resistances.

• So,in series combination, we get maximum resistance.
• In parallel combination, we get minimum resistance.

So, Maximum resistance = 4 + 8 = 12 ohm.

Minimum resistance = 4 × 8/4 + 8 = 8/3 ohm.

Answer 2

Answer:

Explanation:

To get maximum resistance.

Resistances should be connected in series

Request = R1 + R2

= 4Ω + 8Ω = 12Ω

To get maximum resistance.

Resistances should be connected in parallel

1/Req = 1/R1 + 1/R2

= 1/4 + 1/8

= 3/8

Request = 8/3 Ω