electricity

Question 1

what is the equation for current, using: Q and t?
ELECTRICITY

Answer 1

I = Q / t

Question 2

what is the equation for voltage, using: E and Q?
ELECTRICITY

Answer 2

V = E / Q

Question 3

what is the equation for ohm’s law?
ELECTRICITY

Answer 3

V = IR

Question 4

what is the equation for resistivity?
ELECTRICITY

Answer 4

RA = Lρ

(think RALp)

where:
• R = resistance
• A = cross-sectional area
• L = length
• ρ = resistivity

units: Ωm

Question 5

what is the equation for resistors in series?
ELECTRICITY

Answer 5

RT = R1 + R2 + …

Question 6

what is the equation for resistors in parallel?
ELECTRICITY

Answer 6

1 / RT = (1 / R1) + (1 / R2) + …

Question 7

what is the equation for electrical power, using: I and V?
ELECTRICITY

Answer 7

P = IV

Question 8

what is the equation for electrical power, using: I and R?
ELECTRICITY

Answer 8

P = (I^2)R

Question 9

what is the equation for electrical power, using: V and R?
ELECTRICITY

Answer 9

P = V^2 / R

Question 10

what is the equation for EMF, ε, using: V, I and r?
ELECTRICITY

Answer 10

V = ε - Ir

where:
• V = voltage in circuit
• ε = total voltage supplied to circuit from power supply
• I = current of circuit
• r = internal resistance of power supply

Question 11

what is the equation for EMF, ε, using: I, R and r?
ELECTRICITY

Answer 11

ε = I(R + r)

where:
• I = current of circuit
• R = resistance in circuit
• r = internal resistance of power supply

Question 12

what is the equation for EMF, ε, using: V and Vlost?
ELECTRICITY

Answer 12

V = ε - Vlost
or
IR = ε - Ir

where:
• V = voltage in circuit
• ε = EMF
• Vlost = voltage lost in battery [or power supply] due to internal resistance

Question 13

what is the equation for drift velocity?
ELECTRICITY

Answer 13

I = nAev

where:
• I = current in circuit
• n = charge carrier density or number density of electrons
• A = cross-sectional area
• v = drift velocity (which is how fast electrons are moving through a wire)