How much energy, in kWh, is used if a hair dryer with a power of 20 watts was used for 0.5 hours? (Remember to convert to kW first)

0.01kWh

Explanation:

Given parameters:

Power  = 20watts

Time = 0.5hrs

Unknown:

Energy of other dryer  = ?

Solution:

The electrical energy of the dryer can be calculated using the expression below;

  Electrical energy  = IVt

 P  = IV

I is the current

V is the voltage

t is the time

P is the power

  Convert 20watts to kilowatts;

         1000watts  = 1kW

          20watts  =   = 0.02kW

  Electrical energy  = 0.02kW x 0.5hr = 0.01kWh

the density of gold = 19.3 g/cm3

the relation between density and mass and volume is

density = mass / volume

given :

mass of gold = 13 g

density = 13g / volume = 19.3

volume = 13 /19.3 = 0.67 cm^3

thus volume of gold nugget = 0.67 cm^3

c-14 is carbon-14, or radiocarbon.   it is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons.