COE/DC Flashcards
Electric current is
The rate of flow of charge
Formulas for current (there are 2)
Q/t
nAVdq
Potential difference between two points in a circuit is
The amount of electrical energy per unit charge converted to other forms of energy when charge passes from one point to another
One volt is
The potential difference between two points in a circuit when one joule of electrical energy as one coloumb of charge passes from one point to another
formula for volt
V - W/Q
Electromotive force of a source is
The amount of electrical energy per unit charge that is converted from other forms of energy when the source drives a unit charge around a complete circuit.
Formula for electromotive force
E = W/Q
Power is
The rate at which work is done
Formula for power
W = IV = I^2R = V^2/R
Resistance is
The ratio of the potential difference across the object to the current flowing through it
The Ohm is
The resistance of a conductor when a potential difference in a conductor is proportional to the electric current passing through it, provided its temperature remains constant.
Ohm’s law
The potential difference in a conductor is proportional to the electric current passing through it, provided its temperature remains constant.
Formula for resistivity of a wire
R = pA/l so p = Rl/A
Define resistivity of a wire
- The property of a material to oppose electric current.
- The constant of proportionality that relates resistance of a component to it’s length to cross sectional area ratio.
- Constant at a certain temperature, independent of dimensions.
Series arrangement
I1 = I2 = I3
E = V1 + V2 + V3
R = R1 + R2 + … + Rn
Parallel arrangement
I = I1 + I2 + I3
E = V1 = V2 = V3
R is that one complicated to type formula
How does a Thermistor work
Resistance DECREASES when temperature INCREASES
How does an LDR work
Resistance DECREASES when light intensity INCREASES
One coloumb is
The amount of electric charges that passes through a point in one second when there is a constant current of one ampere.
Derive the current carried by a conductor, I = nAvdq
I = ΔQ/Δt = (ΔN)q/Δt = (nΔv)q/Δt = (nAΔx)q/Δt = nAVdq
Derive power (electrical derivation)
P = dW/dt = d(QV)/dt = dQ(V)/dt = IV
Derivation of resistance in series circuits
IE = I² (R1 + R2 + R3)
E = I (R1 + R2 + R3)
E = V1 + V2 + V3
ΣE = ΣV = ΣIR
IReff = IR1 + IR2 + IR3
Reff = R1 + R2 + R3
