More on power

• What does the power of a device indicate?

  Energy transferred per second
• What does potential difference represent in electrical systems?

  Energy transferred per charge passed
• What happens to energy when an electrical charge goes through a change in potential difference?

  Energy is transferred to the charge
• Where does the energy supplied to the charge come from?

  From the power source
• What does the charge do when it 'falls' through a potential drop in the circuit?

  It gives up energy
• What is the formula for energy transferred?

  E = QV
• What do the variables in the formula E = QV represent?

  Energy transferred, charge flow, potential difference
• What does a battery with a bigger potential difference do?

  Supplies more energy per coulomb of charge
• If a motor in an electric toothbrush is attached to a 3 V battery and 140 C of charge passes through, what is the energy transferred?

  420 J
• How can the power of an appliance be calculated?

  Power = Potential difference × Current
• What is the formula to find current if power and potential difference are known?

  I = P ÷ V
• If a 1.0 kW hair dryer is connected to a 230 V supply, what is the current through the hair dryer?

  4.34 A
• What is the rearranged formula for current in terms of power and voltage?

  I = P ÷ V
• What is the relationship between power, current, and resistance?

  P = IR
• In what unit is power measured?

  Watts (W)