Chapter 9 - Energy, Power and Resistance Flashcards
Define potential difference
Work done per unit charge moved.
Define resistance
A measure of a component’s opposition to the flow of current.
Define 1 ohm
The resistance of a component when a P.D. of 1V makes a current of 1A flow through it.
Define the resistivity of a material
The resistance of a 1m length of the material with a 1m² cross-sectional area.
What is ohm’s law?
At a constant temperature, the current through an ohmic conductor is directly proportional to the potential difference across it. (V=IR)
Define power
The rate of transfer of energy.
Define electromotive force (EMF)
The total amount of work the battery does on each coulomb of charge (measured in volts).
What does a steep gradient mean on a graph of I against V?
Low resistance.
What is the difference between EMF and potential difference?
EMF is when work is done to charge carriers, PD is when work is done by charge carriers.
What equation can we use to calculate an electron’s gain in kinetic energy?
eV=1/2mv²
How does light intensity affect the resistance of an LDR?
Greater intensity = lower resistance.
How does temperature affect resistivity in metals & semiconductors?
Higher temperature increases resistivity.
How does resistance vary for an NTC thermistor?
Resistance decreases as temperature increases.
