Physics chapter 13

What is electric current

The flow of electric charge through a conductor

What is the unit for electric charge?

ampere

What is the formula for electric charge?

I = Q/t

I- electric current

Q - the charge

T - time

What is voltage? (Electric potential difference)

The work done to move a unit charge between two points

What is the symbol for voltage

V

What is the formula for voltage?

V = IR

I - current amperes

R - resistance (ohms)

What is the formula for power and current?

V= P/I

P - power (Watts)

I - current ( amperes)

What is the formulas for voltage across a capacitator

V = Q/C

Q- charge (coulombs)

C- capacitance

What is resistance?

Opposition to the flow of electric current in a. Conductor

What is the symbols for resistance

Ohm (omega)

What is the formula for resistance (Ohm’s Law)

I = V/R

R- resistance (ohms)

V- voltage

I - current (amperes)

What is Ohms Law

The current through a conductor is directly proportional to the voltage across it and inversely proportional it its resistance

What is power in electric circuits

The rate at which electrical energy is transferred or converted

What is the symbol for energy that is transferred and converted

Watt (W)

What is a series circuit?

A circuit where there is no points in the circuit where the current can branch into side streams or secondary loops. All elements line up in a single loop.

What is resistance

Property that restricts the flow of one current. The ratio of the electric potential to the current for a given portion of a circuit

What is the formula for resistance?

R = V/I

What is electromotive force

It is not a force. The increase in potential energy per unit charge provided by the chemical reactions in the battery. The voltage of the battery is the electromotive force. Electromotive force is a potential difference and it is measured in colts

What happens when a battery died

As a battery gets older, its internal resistance gets larger and larger. the total resistance of the circuit increases and reduces there current flowing through the circuit. As the current gets smaller the bulb gets dimmer

What are the two types of circuits

Series and parallel

What is a series circuit?

Not as bright

More bulb = more resistance

If one goes out they all go out

A circuit connected in a single loop, so that current passes through each component in succession

What is resistance in a series circuit

Each resistance contributes to restricting the flow of current around the loop

What is the resistance rule in a series circuit

Total = R1+ R2 + R3 …etc.

The same current must pass through each resistance component

What is the formula or rule for current total in a series circuit?

I total = I1 = I2 = I3 … etc.

All has to equal the same

What is the rule for voltage in a series circuit

Voltage changes as current flows through the circuit

The voltage difference across the combination is the sum of the individual changes

V= V1 +V2 +V3… etc

What is a parallel circuit?

Bright, less resistive, of one goes out the others are unaffected

A parallel circuit is a circuit element connected by one more than one path

• circuits are not all in a line around the loop

• They are connected parallel to each other

• There are multiple loop paths

What is the resistance in a parallel circuit?

Rtotal = 1/R1 + 1/R2 + 1/R3…etc

What is the current in a parallel circuit

Itotal parallel = I1 + I2 + I3…etc

The current adds to give the total current through the combination

The current splits up and recombines

A portion of the total current flows through each branch

What is the voltage in a parallel circuit?

The voltage across each resistance is the same

Vtotal parallel = V1 =V2 = V3 …etc.

What is power

The rate of doing work or using energy; the amount of energy per unit of time

What is the formula for power

P = eI

Energy/time

How can we distribute and use electric power

When we use electricity, we use electric power

This power does not come from a battery, but from lines that deliver power from a distance generating source

Electric power can easily be transmitted over considerable distances, which is an advantage to this form of energy

What energy sources are involved when we use electric power?

PE of water behind a dam (gravitational)

PE stored in fossil fuels, like coals, oil, or natural gas (chemical)

PE stored in uranium (nuclear)

What are the two types of currents

Direct current and alternating current

What is direct current

Current that flows in a single direction from the positive terminal to a battery or power supply to the negative terminal

What is an alternating current

Current that continually changes direction when it flows. Alternating current flows in one direct, then reverses and goes in the opposite direction, reverses again… and repeats this cycle over an over again

The alternating current in North America has a frequency of 60 Herts - it goes back and forth 60 times each second

The average value of an ordinary alternating current is 0/