Electricity Flashcards
(36 cards)
What is electric current?
The rate of flow of charge, measured in amperes (amps)
Define potential difference.
The work done moving a unit charge between 2 points in a circuit. V = W / Q
What is resistance?
How difficult it is for current to flow through an appliance. R = V / I
What is an ohmic conductor?
A conductor that obeys Ohm’s law, where current is directly proportional to potential difference under constant physical conditions
How is current measured in a circuit?
With an ammeter connected in series with the component
How is potential difference measured?
Using a voltmeter, connected in parallel across the component being measured
What does the gradient of a current-potential difference graph represent?
The rate of change of current with respect to voltage, not the same as 1/R
What does an ohmic conductor graph look like?
It has a constant gradient and passes through the origin, showing voltage is directly proportional to current
What happens in a higher resistance graph compared to a lower resistance graph?
A higher voltage is required for the same change in current
What is a common appliance that demonstrates a current-voltage curve?
A filament lamp, where increased current leads to increased resistance
What effect does an increase in current have on the resistance of a filament lamp?
Resistance increases as electrical energy is converted to heat energy, impeding electron movement
What is a diode?
A semiconductor device that allows current to flow in one direction only
What assumption should be made about voltmeters?
They have infinite resistance
What is the significance of the ammeter’s resistance?
It should be assumed to have 0 potential difference across it, affecting the circuit minimally
What is a Light Dependent Resistor (LDR)?
A semiconductor sensitive to light, where resistance decreases as light intensity increases
What is a thermistor?
A semiconductor that decreases resistance as temperature increases, having a negative temperature coefficient
Define resistivity.
The resistance of a 1m cylinder with a cross-sectional area of 1m², an inherent property of a material. ρ = RA/L
What is the first step in an experiment to determine the resistivity of a metal?
Measure the diameter of the wire with a micrometer and calculate the cross-sectional area
What is a superconductor?
A material with zero resistivity at or below a critical temperature
How do you find total resistance in a series circuit?
RTotal = R1 + R2 + R3 + …
What is the voltage in a parallel circuit with 6 cells of 5V each?
The voltage in the circuit is 5V
What is the voltage in a series circuit with 6 cells of 5V each?
The total voltage provided to the circuit is 30V
What can be said about current in a series circuit?
The current through all components is the same
