Question

A 2 ohm and 2/3 ohm resistor are connected in parallel across 3v battery. what energy is given out per minute ?

A. 4080 J B. 3080 J
C. 2080 J D. 1080 J

Answer 1

Net resistance = (2 × (2/3)) / (2 + 2/3) = 0.5 Ω

P = V^2 / R
= 3^2 / 0.5
= 18 Watt

Energy given out per minute = P × 60
= 18 × 60
= 1080 J

Answer 2

Answer:

The energy is given out per minute = D. 1080 J

Explanation:

• Equivalent resistance: R1 = 2 ohm and R2 = 2/3 ohm

        R1 and R2 are parallel. If equivalent resistance is R.

        Then $\frac{1}{R}$ = $\frac{1}{R1}$ +  $\frac{1}{R2}$ =  $\frac{1}{2}$ +  $\frac{3}{2}$ =  $\frac{4}{2}$ = 2 ohm

         R = 1/2 = 0.5 ohm

• Potential difference = V = 3 V
• Current, I = V/R  (from Ohm's law)

                      I = 3/0.5 = 6 A

• Time, t = 1 min = 60 sec.

• Energy, E = I²Rt = 6² × 0.5 × 60 J

                                   = 36 × 30 J

                                   = 1080 J

   ∴ 1080 J energy will be given out per minute.