Two resistors of resistance 3 ohm and 6 ohm are connected in parallel to a cell of emf 1.5 V

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Two resistors of resistance 3 ohm and 6 ohm are connected in parallel to a cell of emf 1.5 V

Try the new Google Books

Check out the new look and enjoy easier access to your favorite features

Two resistors of resistance 3 ohm and 6 ohm are connected in parallel to a cell of emf 1.5 V

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Two resistors of resistance 3 ohm and 6 ohm are connected in parallel to a cell of emf 1.5 V

Physics

(a) Given,

e.m.f. = 15 V

internal resistance r = 3 Ω

current through battery = ?

If Rp is the equivalent resistance of resistors 3 Ω and 6 Ω connected in parallel, then

1Rp=13+161Rp=2+161Rp=361Rp=12⇒Rp=2Ω\dfrac{1}{Rp} = \dfrac{1}{3} + \dfrac{1}{6} \\[0.5em] \dfrac{1}{Rp} = \dfrac{2 + 1}{6} \\[0.5em] \dfrac{1}{Rp} = \dfrac{3}{6} \\[0.5em] \dfrac{1}{Rp} = \dfrac{1}{2} \\[0.5em] \Rightarrow R_p = 2 ΩRp1=31+61Rp1=62+1Rp1=63Rp1=21Rp=2Ω

From relation,

ε = I (R + r)

Substituting the value in the formula above we get,

15 = I(2 + 3)⇒ 15 = I x 5

⇒ I = 15 / 5 = 3 A

Hence, current through the battery = 3 A

(b) Potential difference between the terminals of the battery = ?

Using Ohm's law

V = IR

R = 2 Ω

I = 3 A

Substituting the values in the formula above we get,

V = 3 x 2 = 6 V

Hence, potential difference between the terminals of the battery = 6 V

(c) Current in 3 Ω resistor = ?

Using Ohm's law

V = IR

R = 3 Ω

V = 6 V

I = ?

Substituting the values in the formula above we get,

6=I×3I=63⇒I=2A6 = I × 3 \\[0.5em] I = \dfrac{6}{3} \\[0.5em] \Rightarrow I = 2 A6=I×3I=36I=2A

Hence, current in 3 Ω resistor is 2 A

(d) Current in 6 Ω resistor = ?

Using Ohm's law

V = IR

R = 6 Ω

V = 6 V

I = ?

Substituting the values in the formula above we get,

6 = I × 6
⇒ I = 6 / 6 = 1 A

Hence, current in 6 Ω resistor is 1 A