Electricity Flashcards
What is Ohm’s Law?
At a constant temperature, current and voltage are directly proportional.
What law explains that current is the same throughout a series circuit?
The conservation of charge: as charge cannot be created nor destroyed, so the rate of charge entering a point on the circuit must equal the rate of charge leaving that point.
What three physical factors affect the resistance of a stretch of wire?
- Length
- Cross-sectional area
- Resistivity
What is the electromotive force of a power supply?
The electromotive force is the amount of energy transferred to each Coulomb of charge that passes through it.
What is the terminal potential difference of a power supply?
The actual p.d. produced across the terminals of the power supply that is provided to the rest of the circuit.
What is a semiconductor?
A component that can change its resistance based on external conditions.
How do thermistors work?
As temperature increases, more conduction electrons are liberated, meaning there are more available charge carriers, increasing the ability for current to flow.
What’s the standard answer for the potentiometer questions?
- When at one side, p.d. is negligible
- When at other side, p.d. is source voltage
- As slider moves from one side to other side, p.d. increases, as it is shared between the ratio of resistances on either side of the slider
How does conservation of energy explain p.d. distribution?
Energy cannot be created nor destroyed, so the sum of the potential rises and potential drops in any closed loop must equal zero.
What changes that alters the resistance of thermistors and LDRs?
The number of conduction electrons.
What does an oscilloscope trace look like with the time base turned off?
A vertical line in the centre with a magnitude of the amplitude.
What’s the circuit symbol for a heater?
A resistor with perpendicular lines through it.
