A power point for Conceptual Physics Only

1. Electromotive Force (EMF)
 The maximum potential difference
between the + and ‒ terminal
Symbol = E

2. Voltage, Current, & Resistance
Potential Difference [V] (Volt, v)
 charge will only flow when there is a difference in
potential (voltage) across a conductor
ex. Van de Graaff generator sparks but evens out
Voltage causes electrons to flow.
Current [I] (Amperes, Amps, A)
 the flow of e’s I = ∆Q / ∆t
1 Amp = 1 C / 1 s
Resistance [R] (Ohms, Ω)
 resists the flow of electrons (friction)

3. Georg Simon Ohm (German)
Ohm’s Law
 voltage makes the e’s want to flow (Current),
resistance makes them not want to (Resistance)
Which of Newton’s laws does this sound like?
Current = Voltage / Resistance
ex. What is the resistance of an electric frying pan that
draws 12 amps of current when connected to a 120 v
circuit?
I = 12 amps V = I R
V = 120 v 120 = 12 R
R=? R = 10 Ω

4. Electric Power
Electric Power
 The rate at which electric energy is converted into any
other energy
P=IV
Electric Power = Current x Voltage
1 watt = 1 amp x 1 volt = C/s x J/C = J/s
Usually measured in kilowatts. (But must be in watts in
the equations.

5. Is kilowatt – hour a measure of power?
Unit of energy: measures the # of kilowatts
consumed in 1 hour.
This is what the electric company measures off
your meter!