Voltage: the electric potential in a circuit that provides electric pressure to push electrons through the circuit. A voltage source, like a battery or cell, creates a potential difference that moves these electrons. Voltages is measured in _______
Resistance Electric resistance: the resistance of an object to the flow of electric charge through it Like friction for particles! conversion of energy into heat
Example When a conductor has a potential difference of 110 volts placed across it, the current through it is 0.50 ampere. What is the resistance of the conductor?
Resistivity (ρ) Property of a material that affects its resistance resistivity, resistance
Resistance Resistivity Length of the conductor Cross-sectional area
Example What is the resistance at 20°C of an aluminum wire that is 0.2 meter long and has a cross sectional area of 1.00 x 10 -3 square meter? (ρ= 2.65 x10 -8 Ωm)
What do we use to measure the current in a circuit? An ammeter is placed in a circuit to measure the current. It must be in the path of the current, so that nothing flows without going through the ammeter.
What do we use to measure voltage in a circuit? A voltmeter is placed across a circuit component to measure the voltage. Voltage does not flow; we measure the potential difference across a component to see the push each coulomb of charge feels to move through it.
The diagram below represents a simple electric circuit. How much charge passes through the resistor in 2.0 seconds? 1)4.0 C3) 8.0 C 2)2.0 C4) 6.0 C
Example If I have a circuit hooked up to a 6-V power source, and the light bulb has a resistance of 2 Ω, find the value of the current.
1) If a 12-volt battery is hooked up to a light bulb and 2.5 amperes of current flow, calculate the resistance of the light bulb. 2) How much voltage is required for 0.02 A to flow through a resistor of 250 Ω? 3) How much current will flow through a 100-ohm resistor if it’s drawing from a source of 120 volts?
In a simple electric circuit, a 110-volt electric heater draws 2.0 amperes of current. The resistance of the heater is 1)220 ohms2) 28 ohms 3) 55 ohms4) 0.018 ohms
A 9.0-volt battery is connected to a 5.0- ohm resistor as shown below. What is the current through the resistor? 1)9.0 A2) 5.0 A 3) 1.8 A4) 0.55 A