P2: Energy Transfers Physics GCSE

• What is power defined as in electrical terms?

  The rate of energy transfer per second
• What factors does the power of a device depend on?

  Voltage and current of the device
• What is the formula for power in electrical components?

  P = VI
• What is the unit of power?

  The watt (W)
• How is one watt defined in terms of joules?

  One watt equals one joule per second
• How does voltage across an electric device relate to current and resistance?

  It depends on the current and resistance
• How can power be expressed in terms of resistance?

  P = I^2R
• What is the potential difference through a 48 W motor with a current of 4 A?

  12 V
• What is the formula to calculate power through a resistor?

  P = I^2R
• What is the power through a 20 Ω resistor with a current of 6 A?

  720 W
• What mnemonic helps remember the power equation?

  Twinkle Twinkle Little Star
• What does the energy transferred by an appliance depend on?

  Time switched on and power of appliance
• How much energy does a 1 kW iron use in 1 hour?

  1 kWh
• How does energy transfer occur in a heater?

  Energy is transferred to thermal stores
• What happens as charge flows around a circuit?

  Energy is transferred from power source
• What type of energy do motors transfer energy to?

  Kinetic energy store
• What is the function of a vacuum cleaner motor?

  To create suction for dust and dirt
• What is the function of a washing machine motor?

  To rotate the drum for washing clothes
• What is the function of a refrigerator motor?

  To compress refrigerant into a liquid
• How does a toaster transfer energy?

  By heating to toast bread
• How does a kettle transfer energy?

  By boiling hot water
• How does a radiator transfer energy?

  By pumping hot water to heat a room
• What is the equation for energy transferred in electrical work?

  E = P × t
• What does the energy transferred depend on in a component?

  Current, potential difference, and time
• How can energy transferred be calculated using current and potential difference?

  E = I × V × t
• What does E = Q × V represent?

  Energy transferred depends on charge and voltage
• What happens when charge flows around a circuit?

  Energy transferred equals energy to components
• What is the energy transferred in 1 minute with a current of 0.7 A and potential difference of 4 V?

  168 J
• What is the power rating of an appliance?

  Energy transferred by electrical work per second
• What information is included on an appliance's power rating label?

  Voltage, frequency, and power rating
• What happens if an appliance is plugged into a higher voltage supply?

  It may fuse or catch fire
• What does the National Grid do?

  Distributes electricity across the UK
• What are step-up transformers used for?

  To increase voltage and reduce current
• What are step-down transformers used for?

  To decrease voltage for domestic use
• How does the National Grid increase efficiency?

  By using step-up transformers to reduce current
• What is the relationship between potential difference and current in the National Grid?

  High potential difference means low current
• How does a step-up transformer improve energy transfer?

  It reduces heating due to lower current
• What type of current is produced in power stations?

  Alternating current (AC)
• What are transformers made of?

  Two coils of wire around a magnetic core
• How does a step-up transformer differ from a step-down transformer?

  Step-up has more turns on secondary coil