Potential Difference Current and Resistance Voltage Current Resistance

Potential Difference, Current and Resistance • • Voltage Current Resistance How to Measure Voltage, Current and Resistance

Potential Energy = the energy stored in an object • Every electron has potential energy

Potential Difference or Voltage (V) = The source of energy in a circuit provides energy to the electrons. Voltage is described as the force that moves electric charges in a circuit. It is how much energy that the electrons pick up from the source.

Measuring Potential Difference Volt (V) – is the unit used to measure potential difference Voltmeter • Measures the potential difference between two locations in a circuit • A voltmeter is connected in parallel

Electrical Current = is the number and speed of the electrons that are moving through the circuit.

Measuring Current The electric current is measured in units called – Ampere (A) The symbol for current is I Ammeter- measures current in a circuit. An ammeter is connected is series.

Resistance Electrons are very small particles. They move very quickly through a circuit but can sometimes be slowed by larger objects that get in their way (like the nuclei of atoms). The ability to slow the movement of electrons in a circuit is called Resistance. ALL SUBSTANCES RESIST ELECTRON FLOW • Conductors have low resistance values • Insulators have high resistance values

The loads in a circuit tend to have high resistance, to slow the electrons and convert the energy into a useable form of energy. • A Light Bulb Filament has a high resistance.

Resistors • Resistors can be used to control current or potential difference in a circuit • The amount of resistance in a circuit affects the electrical current – Current decreases if you add resistance

Factors Affecting Resistance Table 11. 1: Page. 443 Factor How Factor Affects Resistance Material • The material used in a circuit effects the resistance on the circuit • Copper is used most frequently as conducting wire Temperature • High temperatures have a higher resistance • Low temperatures have a lower resistance Length • Longer wires have more resistance • Shorter wires have less resistance Cross-sectional Area • Wide wires have less resistance • Short wires have more resistance

Measuring Resistance Ohm (Ω) – the unit used to measure resistance The symbol for resistance is R Ohmmeter • Measures electrical resistance

Homework A. Questions 3 -5 pg. 438 B. Questions 1 -3 pg. 442 C. Questions 3, 4, 5, 7, 8, 10 pg. 447