Ch. 21 - Electricity

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# Ch. 21 - Electricity - PowerPoint PPT Presentation

Ch. 21 - Electricity. II. Electric Current (p.598-599) Circuit Potential Difference Current Resistance Ohm’s Law. A. Circuit. Circuit closed path through which electrons can flow. A. Potential Difference. Potential Difference (voltage)

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### Ch. 21 - Electricity

II. Electric Current

(p.598-599)

Circuit

Potential Difference

Current

Resistance

Ohm’s Law

A. Circuit
• Circuit
• closed path through which electrons can flow
A. Potential Difference
• Potential Difference (voltage)
• difference in electrical potential between two places
• large separation of charge creates high voltage
• the “push” that causes e- to move from - to +
• measured in volts (V)
B. Current
• Current
• flow of electrons through a conductor
• depends on # of e- passing a point in a given time
• measured in amperes (A)

Copper - low resistance

Tungsten - high resistance

C. Resistance
• Resistance
• opposition the flow of electrons
• electrical energy is converted to thermal energy & light
• measured in ohms ()
C. Resistance
• Resistance depends on…
• the conductor
• wire thickness
• less resistance in thicker wires
• wire length
• less resistance in shorter wires
• temp - less resistance at low temps
E. Ohm’s Law
• Ohm’s Law

V: potential

difference (V)

I: current (A)

R: resistance ()

V = I × R

• Voltage increases when current increases.
• Voltage decreases when resistance increases.

V

R

I

E. Ohm’s Law
• A lightbulb with a resistance of 160  is plugged into a 120-V outlet. What is the current flowing through the bulb?

GIVEN:

R = 160 

V = 120 V

I = ?

WORK:

I = V ÷ R

I = (120 V) ÷ (160 )

I = 0.75 A