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 Battery Longer 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 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?