Question

Physics - hair dryer problem - multiple partsKilowatts-hours, power, etc…

Answer 1

Explanation

Step 1

a)Power

this is an electric power measure of the rate of electrical energy transfer by an electric circuit per unit time,it is given by the expression

$\begin{gathered} P=VI \\ (\text{unit; watt ot }\frac{joule}{s}) \\ \text{where v is the voltage and I is the current} \end{gathered}$

then

Let

V= 120 v

I=15 A

now,replace in the formula

$\begin{gathered} P=VI \\ P=120v\cdot15A=1800\text{ J} \\ P=1800\text{ Joules} \end{gathered}$

therefore, teh answer is

a) 1800 Joules

Step 2

if runs for 3 minutes

how many joules of energy

Power can be expressed as P = Work/Change in Time}

so

$\begin{gathered} \text{work = Power }\cdot\text{ time} \\ \text{work = 1800 Joules}\cdot180\text{ s=}324000\text{ joules} \end{gathered}$

so

b)324000 Joules

Step 3

c)Kilowatt -hour

to do this conversion of units, we need to know the equivalence:

$\begin{gathered} 1\text{ Kwh= }3600000\text{ Joules} \\ so \\ 324000\text{ Joules(}\frac{1\text{ kw hour}}{3600000}\text{)=}0.09\text{ Kwh} \end{gathered}$

so

c) 0.09 Kw-h

I hope this helps you