Download Electricity Review

Electricity Review
Static Electricity –
1.6 x 10-19 C = 1 e
1.6 x 10-19 J = 1 eV
You must plug in coulombs into a formula!
Proton = +1 e or + 1.6 x 10-19 C
Electron = -1 e or -1.6 x 10-19 C
Neutron = 0 e or 0 C
Alpha Particle = +2 e or +3.2 X 10-19
Elementary charges to Coulombs: Multiply by 1.6 x 10-19 C
Coulombs to Elementary Charges: Divide by 1.6 x 10-19 C
Electrostatic Force:
Fe = kq1q2/r2
k = 8.99 X 109 (electrostatic constant)
F is directly related to q
F is inverse squared related to r
Electric Field Strength
Magnitude:
Direction:
E = Fe/q
Out of the positive into the negative
 KNOW THE SIX PICTURES OF ELECTRIC FIELD LINES IN
YOUR WORKBOOK!!!!!!!
(Page 119)
Parallel plates: The lines are uniform, therefore the force
in any place between the two plates are constant.
E = V/d (Parallel Plates)
Electric Energy and Potential Difference
V = W/q
If the work is measured in J, then q must be in Coulombs.
(V is always Volts)
If the work is measured in eV, then q must be in elementary
charges
(V is always Volts)
Circuits:
V = IR
Series Circuits
 Voltage is additive (V)
 Current is constant (I)
 Equivalent resistance is additive (Req)
Parallel Circuits
 Voltage is constant
 Current is additive
 Equivalent Resistance is reciprocal
Adding resistors to a series circuit will decrease the current and
increase the total resistance
Adding resistors to a parallel circuit will increase the current
and decrease the total resistance. (overloading)
Voltmeters must be places in parallel in order to be used within
a circuit
Ammeters must be place in series in order to be used within a
circuit.
P = VI = I2R = V2/R
Since W = PT
W =VIt = I2Rt = (V2/R)t
Resistance of a Wire
𝑅=
𝜌𝐿
𝐴
ρ= is the restitivity of the metal
L is the length
A is the cross sectional area
Restitivity depends on the metal used and the temperature.
Restitivities at 20о C are given on the chart on reference table.
An increase in Temperature will increase the restitivity and
therefore increase R (for everything except carbon) (and visa
versa)
An Increase in Length will increase R (and visa versa)
An Increase in Area will decrease R (and visa versa)
Magnetism
Magnetic Flux Density (Magnetic Field Strength) (B)
The more lines per unit area, the stronger the field strength
North Pole, South Pole
Magnetic Field lines always run from N to S. Memorize pictures
on p 134.
Electromagnetic Induction
Moving a wire through a magnetic field will induce a voltage
(and therefore a current) through the wire
Left hand rule for induction:
Fingers go in the direction of the magnetic field (N to S)
Thumb points in the direction of the current
Palm faces the direction of movement of the wire.