Electric Current Flashcards
Which way does current flow around a circuit?
Positive to negative.
Define current.
The rate of flow of charge in a wire or component or circuit.
Define voltage/potential difference?
The work done per unit charge (1 Volt = 1 Joule/Coulomb) (V=W/Q) .
Define emf.
The emf of a source of electricity is defined as the electrical energy produced per unit charge passing through the source.
What two effects does an electric current have when it passes through a component with resistance?
A heating effect and a magnetic effect.
Define resistance.
The resistance of a component is a measure of the difficulty of making a current pass through the component. It is defined as the pd across the component divided by the current through it.
What is Ohm’s Law?
Ohm’s Law states that the pd across a metallic conductor. Is proportional to the current through it, provided the physical conditions do not change.
What equation links resistivity to resistance, cross sectional area and length?
R = ϱL/A
What is the unit of resistivity?
Ωm
What equation for cross sectional area should you use in physics to limit uncertainty?
πd²/4
Around what pd does a diode change its conductivity?
0.6 Volts
What relationship is there between resistance of a component and temperature, and why is this the case?
The resistance of a metal increases with the increase of temperature. This is because the positive metal ions in the conductor vibrate more when it’s temperature is increased.
