Electric Resistance What is Resistance Resistance is the

Electric Resistance

What is Resistance? Resistance is the extent to which a conductor or insulator resists the flow of current. It is a property of a substance that prevents the motion of electricity and converts electrical energy to other forms of energy, such as heat. Good conductors therefore have low resistance whereas poor conductors have high resistance.

Describing Resistance How much energy does it take to push a 50 Kg crate across a room? • • • This depends on the resistance there is towards the sliding motion. If you are pushing the crate across a carpet, it is going to require a lot of energy because there is much more resistance. If you are pushing it across a tile floor, there is less resistance and therefore less energy is required.

Describing Resistance How does moving through a hallway full of Jell-o affect your motion?

Types of Resistors (loads) Type Heat resistor Light bulbs Motors Energy imput Energy output

Factors Affecting Resistance 1. Length of wire Resistance increases with length. 2. Thickness of Resistance decreases with thickness. wire 3. Temperature Resistance increases as temperature increases. 4. Material Good conductors have low resistance.

Ohm’s Law RESISTANCE, CURRENT, and VOLTAGE can be related using something called OHM’S LAW. Resistance (Ω) = R=V I Voltage (V) Current (A) Units for Resistance are Ohm’s (Ω) Using this formula, we can solve for all three variables: R=V I R V=Ix. R

Ohm’s Law Example One: A series circuit with a 24 V battery operates a space heater that has 2. 62 A of current flowing through it. Find the resistance of the heater.

Ohm’s Law Example Two: A current of 4. 15 A has 625. 13 Ω of resistance. What is the voltage?

Measuring Resistance (Graphing V vs I) Voltage (V) Current (A)_ Resistance (ohms)