Question

A hairdryer transfers 36,000J in one minute, what is the power rating of the hairdryer?

Answer 1

Answer:

1. 600 watts

2. 35640 J

3. 55%

4. 20 J

5. The cost of running the fire is 8p.

Step-by-step explanation:

1. Energy = 36 000 J , t = 1 minute = 60 seconds

Power = $\frac{energy}{time}$

           = $\frac{36000}{60}$

          = 600 watts

2. Power = $\frac{work done}{time}$

⇒ work done = Power × time

                      = 99 × 360

                      = 35640 J

3. Efficiency = (Output / Input) × 100

                    = $\frac{55}{100}$ × 100

                    = 55%

4. Work done = Force × distance

                      = 5 × 4

                      = 20 J

5. Given that 1 KWh cost 2p, Power = 4 KW and time = 4 hours.

  Power = $\frac{energy}{time}$

Energy = Power × time

            = 4 × 4

           = 16 KWh

The cost of running the fire = $\frac{16}{2}$

                = 8p