Physics 2 Exam 3 Prep

I need to pass this.

Current

The Flow of charge through a conductor.

What is Current measured in?

Amperes

Current Density Equation

J=I/A

Kirchhoff's Junction Law

1) The current is the same everywhere in a circuit with no junctions.
2)The sum of currents entering a junction equals the sum leaving.

Resistivity

Is an electrical property of a material.

Resistance

is a property of a specific wire or circuit element based on the material of which it is made and its size and shape.

Ohm's Law

The change in V/R

Current

Motion of charges

Voltage Across Capacitors....

Adds up to the net voltage

If Capacitors are in parallel...

They will have the same voltage

When adding two resistors in series...

The resistance is being increased

When adding two resistors in parallel...

The Resistance is being decreased

What quantity is represented by the symbol J ?

Current Density

The electron drift speed in a typical current-carrying
wire is?

Extremely Slow (≈ 10^–4 m/s).

All other things being equal, current will be larger in
a wire that has a larger value of...

Conductivity

Electrons are the charge
carriers in...

Metals

Electron Current

the number of
electrons per
second that pass
through a cross
section of the
conductor.

When an conductor
is in electrostatic
equilibrium...

there is
no electric field.

The electron current is directly proportional...

to the
electric field strength.

Note that the direction of the current I in a metal is...

opposite to the direction of the electron current ie.

Current Density Units

A/m^2

Due to conservation of charge, the current in a current-carrying wire...

must be the
same at all points

This complete loss of
resistance at low
temperatures is called

superconductivity

The unit of Resistance

Ohm

Circuits

the controlled motion through conductors and resistors

How many laws are named after Kirchhoff?

2

In an RC circuit, what is the name of the quantity represented by the symbol τ?

Time constant

The equivalent resistance for a pair of parallel resistors is?

Less than any resistor in the group

Kirchoff's loop law

The sum of all the potential differences encountered while moving around a loop or closed path is zero.

The power supplied by a battery is

P=Ie

The units of Power

Watts

The power dissipated by a resistor is

P=IV

A current carrying resistor dissipates power because...

the electric force does work on the charges

Resistors that are aligned end to end, with no
junctions between them, are called

Series resistors

Resistors connected at both ends are called

parallel resistors

If a circuit is connected to the Earth through an ideal wire it is said to be...

grounded

RC Circuit

A circuit with both resistors and capacitors

Charge on the capacitor of an RC circuit is

Q0e^-t/τ