Resistors, Capacitors and Inductors

Question 1

What happens to the potential difference across a capacitor as current passes through it? Why? What happens to the potential difference across the resistor?

Answer 1

It increases because it provides resistance to the current
It decreases

Question 2

What is the time constant of a circuit in relation to a capacitor? What is its symbol and unit? What is its equation?

Answer 2

The time it takes for the capacitor to fully charge dependant on the circuit’s components
τ, s (seconds)
τ = C x R
time constant = capacitance x resistance

Question 3

What is the time constant in relation to inductance? What is its equation?

Answer 3

The time it takes for the current to increase to a maximum dependant on circuit components
τ = L / R
time constant = inductance / resistance

Question 4

What is resistivity? What is its symbol? What is its unit?

Answer 4

A material’s ability to oppose/resist the flow of electric current
ρ (rho)
Ωm (ohm-metre)

Question 5

How is resistance calculated (without I or V)?

Answer 5

R = (ρ x l) / A
resistance = (resistivity x length) / cross-sectional area

Question 6

What are variable resistors?

Answer 6

Resistors that can have their value changed manually

Question 7

What are two resistors that change their resistance based on environmental factors?

Answer 7

LDRs (Light-Dependant Resistor)
Thermistor

Question 8

What is the equation for capacitance of a parallel plate capacitor (not relating to quantity or current)?

Answer 8

C = (ε x A) / d
capacitance = (coefficient of permittivity(of dielectric) x area) / separation

Question 9

Which pole of a capacitor is the negative one (cathode)?

Answer 9

The shorter one/the one closer to the negative lead markings