Electrical power and energyIB MYP Physics: Flashcards

What these 14 flashcards ask

What is power?
What is one watt?
State the equation linking power, current and p.d.
State the equation linking power, current and resistance.
State the equation for energy transferred in terms of power and time.
State the equation for energy in terms of current, p.d. and time.
What is a kilowatt-hour?
How do you calculate the cost of electricity?
How do you convert watts to kilowatts?
State the equation for efficiency.
Can an appliance have an efficiency of more than 100%?
What form does wasted energy usually take?
Why does a wire get hot when a current flows?
Give one use of the heating effect of a current.

Exam questions on Electrical power and energy

A café owner in Istanbul buys a new electric kettle. The label on the base states that it is designed for the 230 V mains supply. While testing it, she finds that the kettle draws a steady current of 8.0 A when switched on.
The kettle has a power of 1840 W. Calculate the energy it transfers in 3.0 minutes.2 marks
A family in Cairo has a 2.0 kW air conditioner. They run it for 6.0 hours every day. Their electricity supplier charges 10 cents for each kilowatt-hour (kWh) of energy.
Calculate the cost of running the air conditioner for 30 days.2 marks
A student investigates how efficiently an electric heater warms water. She connects a 12 V heater, which carries a current of 5.0 A, to a beaker of water and switches it on for 5.0 minutes. She then measures how much thermal energy the water has gained.
Calculate the power of the heater and the electrical energy transferred to it in 5.0 minutes.3 marks

Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).