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?