Question

1) An electrical appliance produce 400J heat in 10 second. calculate power?

2)The device of resistances 200ohm in 100V. calculate power?​

Answer 1

Answer:

The power in first case is 40 W

Explanation:

H=$I^{2}$Rt

P = $I^{2}$R

therefore,

400=P*10

P=40 W

Resistance=200Ω

Voltage=100 V

P=VI = V²/R

        = 100 * 100/200

        =50 W.

Answer 2

Answer:

The lamp doesn't have power. It consumes power and outputs lumens of light plus heat energy over the period of time concerned.

Power = Energy / time. So Power consumed = 1000 Joules / 20 seconds = 50 Joules per second.

1 Watt of power is 1 joule per second

Power consumed = 50 Watts

Power usage for consumers is expressed in KW hours So 50 Watts is 0.05 KW in other words 20 of these lamps would need to be lit to consume 1KW of power.

20 seconds is 1/3 of a minute and 0.0055555 hrs. KW hrs = 0.05 x 0.0055555= 0.000277775 KW hours.

An LED bulb provides 100 Lumens of light per watt so the above lamp is what we call a 5k light giving out 5000 Lumens.

An old incandescent bulb gave out 12–17 averaging 14.5 Lumens per Watt.

So if the above bulb was this type it would give out 725 Lumens on average.

Mike

Explanation: