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Physics Definitions and Equations
Everything from 5.1 - 5.5 (excluding HL material from 5.3)
25
Physics
12th Grade
10/17/2011

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Cards

Term
Coulomb's Law
Definition
The electric force between two point charges q and Q is given by

F= kqQ/r^2
Term
Electric force experienced by charge from electric field
Definition
E = F/Q

NC^-1
Term
Electric field at a point
Definition
Ep = kQ/r^2
Term
Potential at a point
Definition
V = W/Q

Measured in Volts, or JC^-1
Term
Potential energy of charge
Definition
U=qV

Measured in Volts
Term
Electric field between parallel plates
Definition
E = V/d

Vm^-1 volt meter
Term
Electronvolt
Definition
1 eV = 1.6 x 10^-19 C x 1 V

Electron charge per 1 volt of potential
Term
A charge q in an electric field of magnitude E will experience a force of magnitude...
Definition
F = qE
Term
Equation for work done in moving a charge q across a potential difference V (delta V)
Definition
W = qV (delta V)
Term
Law of conservation of charge
Definition
1/2mv^2 + qV (A) = 1/2mv^2 + qV (B)

Left hand side is A, right hand side is B
Term
Electric Potential
Definition
The work per unit charge required to bring a positive test charge from far away to the point of interest. (Volts or JC-1)
Term
Equation for potential difference
Definition
Work that must be done to bring a charge q from point A to point B is

W = q x (Vb - Va)
Term
Electric Current
Definition
The amount of charge that moves through the cross-sectional area of a wire per unit interval of time.

I=Q/t
Term
Motion of electrons in current
Definition
Electric field forces electrions to drift in one direction - overwhelming the electrons that collide with atoms and ions from the conductor itself, forcing them to 'drift' in one direction. This is current.
Term
Electric Resistance
Definition
Potential difference across its ends divided by the current flowing through it. Given by:

R = V/I
Term
Ohm's Law
Definition
When the temperature of a metallic conductor is kept constant, the current through the conductor is proportional to the potential difference across it.

I ∝ V

Graph of this will be straight line passing through origin.
Term
Relationship between Resistance, Length and Area
Definition
R ∝ L/A

The electric resistance of a wire is proportional its length L, and inversly proportional to the cross-sectional area A.
Term
Potential drop
Definition
The phenomena that occurs when electric current passes through a resistor; the potential at a point afterward is less than at a point before.

V = IR can be used to find this.
Term
Equation(s) for Electric Power
Definition
P = VI

P = RI^2

P = V^2 / R
Term
emf
Definition
Ratio of work done by non-electrical forces, W, to a quantity of charge q that moves from one terminal of the battery to the other.

Measured in Volts. emf = W/q
Term
Resistances of series circuits
Definition
Are added up; R-total = R1 + R2 + R3 + ...

Can be replaced with one large resistor of R - total
Term
Resistances of parallel circuits
Definition
Circuit splits for the seperate paths with resistors. Law of conservation of charge means charge is same at beginning and end of split.

1/R-total = 1/R1 + 1/R2 + 1/R3 + ...
Term
Ammeters
Definition
Devices used to measure the current (amperes) in a circuit. They must be in series to resistors, and must have zero resistance to work effectively (ideal).
Term
Voltmeter
Definition
A device used to measure the potential difference across a resistor. It must be connected in parallel to the resistor. Ideally, it should have infinite resistance; to take no current when connected to a resistor.
Term
Potential Divider
Definition
A device that is used to determine the current-voltage characteristic of some device with resistance R.

Can affect the amount of current going from different parts of the circuit through adjustment.
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