Electrical power and I-V characteristicsEdexcel A-Level Physics: Flashcards

What these 13 flashcards ask

State the equation for electrical power in terms of p.d. and current.
Give the equation for electrical energy transferred.
Which power equation is best when the current is the same in each component?
Which power equation is best when the p.d. is the same across components?
What does an ohmic conductor's I–V graph look like?
Why does a filament lamp's resistance increase with current?
What happens to the gradient of a filament lamp's I–V graph as p.d. increases?
Why does the resistance of an NTC thermistor fall when it is heated?
How does the I–V graph of an NTC thermistor change as p.d. rises?
At what forward p.d. does a silicon diode begin to conduct?
What is the current in a diode in reverse bias?
How do you find the resistance at a point on a curved I–V graph?
Why can an NTC thermistor connected across a fixed p.d. overheat?

Exam questions on Electrical power and I-V characteristics

An electric kettle is rated 2.3 kW when connected to the 230 V mains supply. Its heating element is a single piece of resistance wire.
The kettle is switched on for 3.0 minutes at its rated power. Calculate the energy transferred by the element. Give your answer in joules.2 marks
A student investigates a filament lamp using a variable power supply. At a p.d. of 2.0 V the current in the lamp is 0.50 A, and at a p.d. of 12 V the current is 1.5 A.
Explain why the resistance of the lamp at 12 V is greater than its resistance at 2.0 V.2 marks
A silicon diode is connected in series with a 220 Ω resistor and a 6.0 V battery of negligible internal resistance. When the diode is forward-biased the p.d. across it is 0.70 V.
Calculate the current in the circuit.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).