A 750 W motor drives a pump which lifts 300 L of water per minute to a height of 6 m. The efficiency of the motor is nearly (Take, acceleration due to gravity to be 10 m / s 2 )

Question

A 750 W motor drives a pump which lifts 300 L of water per minute to a height of 6 m. The efficiency of the motor is nearly (Take, acceleration due to gravity to be 10 m / s 2 ) (A) 30 % (B) 40 % (C) 50 % (D) 20 %

Tardigrade Admin · Accepted Answer

Useful power =( text Work done by motor / text Time duration ) ⇒ P text input × η=(W/Δ t) arrow P text input × η=(m g h/t) ⇒ η=(300 × 10 × 6/60 × 750)=0.4 So, per cent efficiency is, η=40 %

Q. A $750 W$ motor drives a pump which lifts $300 L$ of water per minute to a height of $6 m$ . The efficiency of the motor is nearly
(Take, acceleration due to gravity to be $10 m / s^{2}$ )

$30%$

$40%$

$50%$

$20%$

Useful power
$= \frac{Work done by motor}{Time duration}$
$\Rightarrow P_{input} \times η = \frac{W}{Δ t}$
$\to P_{input} \times η = \frac{m g h}{t}$
$\Rightarrow η = \frac{300 \times 10 \times 6}{60 \times 750} = 0.4$
So, per cent efficiency is, $η = 40%$

Q. A 750W motor drives a pump which lifts 300L of water per minute to a height of 6m. The efficiency of the motor is nearly (Take, acceleration due to gravity to be 10m/s2 )

30%

40%

50%

20%