Voltage, Current, Resistance and Power

Voltage

Voltage is the ____________________________ through an electric circuit.

Voltage is measured in _____ or ______. In an electric circuit the voltage may be

provided by a battery, a voltage source or a potentiometer.

Cell or BatteryLonger Line indicates

positive

Direct Current Voltage Source

Potentiometer

Electric Current

Any flow of charge is called an _________________________.

Current is measured in ________ (_____ or ___). 1 Amp = 1 _____ In electric circuits, we assume it is ________________ flowing

through the circuit (_____________ current). In reality, it is the ___________________. However in gases

and liquids both positive and negative charges can flow.

Example 1: Electric Current

A steady current of 4.7 A exists in a wire for 180-s.

a) How much total charge passed by a given point in the circuit during this time?

b) How many electrons was this?

Electric Circuits

All voltage sources have a ________ “pole” and a ________ “pole”.

A battery produces current by _________ the electrons with the negative pole and __________ electrons with the positive pole.

Current will only be produced if there is a _____ path (_______) for the electrons to flow from the negative pole to the positive pole.

+ -

Conventional Current

I

When there is no closed path, a circuit,

for the electrons to follow from the

negative pole of the voltage source to the positive pole of the

voltage source, ________________ ____________!!!!

But once the path is closed the electrons are repelled by the negative pole of the voltage source and

attracted to the positive pole of the

voltage source.

Example 2: Electric Circuit

Which of the set-ups below will cause the bulb to light?

Resistors & Resistance

A property of all conductors is their ability to _____ the flow of electric current.

This property is called ____________, R.

The units for resistance are ohms, ___. 1 Ω = 1 ______

Resistor

OR

Ohm’s Law

Georg Simon Ohm discovered that the resistance, R, was _______ in many conductors.

This is known as Ohm’s Law. Materials that obey Ohm’s Law are called

__________. Materials that don’t obey Ohm’s Law are called

__________.

Example 3: Ohm's Law

A light bulb has 120-V across it and carries 0.012-A.

a) What is the resistance of the bulb.

b) Find the current through the bulb if the voltage across it is now 80-V.

c) What voltage would be required to push 1.0-A through the bulb?

Electrical Power

Electical Power is measured in _________

If the electrical Device is an Ohmic Resistor:

OR

Example 4: Electrical Power

A light bulb has 110-V across it and a current of 0.5-A through it

a)What is the power of this bulb?

b)What is the resistance of this bulb?