Energy Transfers

• What two main factors does the amount of energy transferred by an appliance depend on?

  How long the appliance is running for

  The power of the appliance
• Describe the energy transfers in a battery powered torch

  Battery converts chemical energy into electrical energy

  Bulb converts electrical energy into light and any wasted energy comes out as thermal
• Describe the energy transfers in a battery powered motor.

  Battery converts chemical energy into electrical energy

  Motor converts electrical energy into kinetic energy as well as waste energy in the form of friction
• What three things determine the power of a circuit device?

  The potential difference across the circuit

  The current through the circuit.

  The amount of energy transferred in a given second.
• What is the National Grid?

  To link power stations to consumers so they have access to a reliable source of electricity.
• What two types of transformers are used in the national grid?

  Step-Up Transformers

  Step-Down Transformers
• Where are step-up transformers found in the national grid, what do they do?

  Step-Up transformers are used when connecting power stations to transmissions cables

  They increase potential difference.
• Where are the step-down transformers found in the National Grid? What do they do?

  Step-Down transformers are used to connect transmission cables to domestic buildings like home

  They decrease potential difference.
• Why do transmission lines transfer electricity at high potentials

  A high potential difference, results in low current

  The lower the current, the less energy wasted by heat

  Therefore, it is more efficient
• Why does the potential difference need to be lowered between house and transmission lines?

  Lower potentials are safer for domestic use and reduces likelihood of severe electrocution

  Appliances designed for 230 V