Question

There are two electric lamps m and n which are joined in a series having resistance equal to 15 ω and 20 ω respectively. if the potential difference between two terminals of electric circuit is 220v, find the total resistance and electric current through the circuit. also find the potential difference across the two lamps separately.

Answer 1

Resistance of lamp m = 15Ω
Resistance of lamp n = 20Ω
Both are joined in series so, Req = R₁ + R₂
Req = 15Ω + 20Ω = 35Ω

Given, potential difference across the circuit = 220V
so, use Ohm's law,
V = iR
Current through circuit , i = 220/35 = 6.28 A

Now, potential difference across lamp m = Resistance of lamp × current
= 15Ω × 6.28A = 94.2V
Potential difference across lamp n = resistance of lamp n × current
= 20Ω × 6.28A = 125.6V

Answer 2

Hello Dear.

Here is the answer---

→→→→→→→→→

Given ⇒

Resistance of lamp m(Rm) = 15 Ω
Resistance of lamp n(Rn) = 20 Ω
Since these are connected in parallels, 
∴ Req = Rm + Rn
           = 15 + 20
           = 35 Ω

Potential Difference between two lamps m and n(V) = 220 V.

Using the Ohm's Law,
 V = I × R
 ⇒ I = V/R
       = 220/35
       = 6.28 A.

We know, Current is same in Series Combination,
∴ For Lamp m,Potential Difference = Current × Resistance(Rm)
 V = 6.28 × 15
    = 94.2 V.

For lam n,Potential Difference = Current × Resistance(Rn)
 V = 6.28 × 20
 V = 125.6 V.

Hope it helps.