Ch 34 &amp; 35 Review

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# Ch 34 & 35 Review - PowerPoint PPT Presentation

Ch 34 &amp; 35 Review. Current and circuits. Units and Symbols. Resistance Current Voltage Power Battery. Types of current in the US. DC Direct current – from a battery, solar panel AC

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Presentation Transcript

### Ch 34 & 35 Review

Current and circuits

Units and Symbols

Resistance

Current

Voltage

Power

Battery

Types of current in the US

DC

Direct current – from a battery, solar panel

AC

Alternating current – electric current repeatedly reverses direction because the voltage polarity continually switches back and forth

In the US, it has a frequency of 60 Hz, in many other parts of the world the frequency is 50 Hz

definitions

Short circuit

a faulty or accidental connection between two points of different potential in an electric circuit, bypassing the load and establishing a path of low resistance through which an excessive current can flow. It can cause damage to the components if the circuit is not protected by a fuse

Closed/open circuit

A closed circuit allows current to flow through the path of wires, an open circuit has a break in the path so no current flows

relationships

What factors affect the resistance of a wire?

What is Ohm’s law

The power equation

How can Ohm’s law be incorporated into the power equation?

Electrical resistance in

Series

RT = R1 + R2 + R3

Parallel

Thick and Thin filament problems

Will a lamp with a thick filament draw more current or less current than a lamp with a thin filament?

One lamp is 60 W and the other is 75W, which has the thicker filament?

Which draws the most current?

If connected in series, which has the most current? Greatest voltage drop?

If connected in parallel, which draws the most current? Greatest voltage drop?

Thick and Thin filament problems

Will a lamp with a thick filament draw more current or less current than a lamp with a thin filament?

Assume same voltage source, 10 V, the larger the area of the wire, the more current it will allow.

One lamp is 60 W and the other is 75W, which has the thicker filament? Draws the most current?

Assume 10 V across each lamp, P=VI, so I=P/V, larger the wattage, the greater the current, greater current means thicker wire

In series, same current through all resistors

With same current, Greater the resistance = greater the voltage drop

If connected in parallel, which draws the most current? Greatest voltage drop?

Voltage same across each branch in parallel,

Higher the resistance of a branch, the lower the current

How voltage changes?

How current changes?