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13.3 to 13.7 Calculating Quantities in circuits

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(1)

Electricity

(2)

Lesson 1

13.3 Electric Current

(3)

Series and Parallel Circuits

In series circuits, current can only take one

path.

The amount of current is the same at all points

(4)

Series and Parallel Circuits

In parallel circuits the current can take more than one

path.

Because there are multiple branches, the current is not

(5)

Series and Parallel Circuits

Sometimes these paths are called branches.

The current through a branch is also called the branch

current.

When analyzing a parallel circuit, remember that the

current always has to go somewhere.

The total current in the circuit is the sum of the currents in

(6)
(7)

Coulombs Law of Charges

Charged bodies attract or

repel each other with force

(8)

Electric Current

Current?

flow

(9)

Electric Current

Movement of electric chargeRate of charge movement

Q

I

t

unit

C

Ampere, A

1A=1

(10)

10 Quantity Physics symbol Measured in unit

Time t seconds s

Current I Amperes Å

(11)
(12)

Complete Worksheet

Current and Charge worksheet

(13)

Lesson 2

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14

Potential Energy (difference)

Voltage and Current are vital to

understanding electronics, but they are quite hard to grasp because we can't see them

directly.

(15)

Voltage is sometimes described as the 'push'

or 'force' of the electricity, it isn't really a force but this may help you to imagine what is

happening.

Voltage is a measure of the energy carried

by the charge.

(16)

Voltage attempts to make a current flow, and

current will flow if the circuit is complete

Will the following circuits work?

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Electric Potential

Any point in an electric field is said to

have Electric Potential, V.

However, only a Difference in PE is

(20)

20

Electric Potential

Voltage is supplied by the battery (or

power supply).

Voltage is used up in components,

but not in wires.

(21)

Electric Potential Difference

Voltage is the amount of energy that is gained by

each electron from a source and lost over a load. It is the difference in electrical potential energy

between two points in a circuit.

The unit is joules per coulomb OR the Volt (V)

unit Volt, V J

(22)

Voltage in a series circuit

Each separate resistance creates

a voltage drop as the current passes through.

As current flows along a series

circuit, each type of resistor

transforms some of the electrical energy into another form of

energy

Ohm’s law is used to calculate the

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(25)

Voltage and current

in a parallel circuit

In a parallel circuit the voltage is the same

across each branch because each branch

has a low resistance path back to the battery.

The amount of current in each branch in a

parallel circuit is not necessarily the same.

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26

Voltage

Voltage is a force that pushes/drives the

electrons/charge

 It is also referred to as electromotive force or

difference in potential.

 Voltage is measured in volts (v)

 Voltage source will have a polarity (negative

and positive side)

 Current flows from negative to positive

(27)
(28)

Advantages of parallel circuits

Parallel circuits have two big advantages over series circuits:

1. Each device in the circuit sees the full battery voltage.

2. Each device in the circuit may be turned off independently without stopping the current

(29)

Complete Worksheet

(30)

Lesson 3

13.7 and 13.9 Resistance

(31)

Analysis of Circuits

Key Question:

(32)

Series and Parallel Circuits

Sometimes these paths are called branches.

The current through a branch is also called the branch

current.

When analyzing a parallel circuit, remember that the

current always has to go somewhere.

The total current in the circuit is the sum of the currents in

all the branches.

At every branch point the current flowing out must equal

the current flowing in.

(33)
(34)

34

Resistance

Resistance is the opposing force to the flow

of electrons through a part of the circuit.

Resistance (R)is the opposition to the flow of

an electric current, causing the electrical

(35)

What is electrical

resistance

?

(36)

36

Ohm’s Law

:

The resistance of an object determines the

(37)

Ohm’s Law

V

IR

Current = voltage/resistance

(38)

38

Resistance

Depends on: Length, cross sectional area,

(39)
(40)

40

(41)

The unit for measuring resistance is the

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42

Resistor

An electronic element

that provides a specified resistance.

A current or voltage

(43)

20.1 Adding resistances in series

Each resistance in a series

circuit adds to the total resistance of the circuit.

(44)
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20.1 Total resistance in a series

circuit

Light bulbs, resistors, motors, and heaters usually have

(46)

Calculate current

How much current flows in a circuit with a 1.5-volt

(47)

Resistance in parallel circuits

Adding resistance in parallel provides another

path for current, and more current flows.

When more current flows for the same

voltage, the total resistance of the circuit decreases.

This happens because every new path in a

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(49)

Adding resistance in parallel circuits

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Ohm’s Law Summary

Quantity Physics Symbol Measured in Unit

Voltage V Volts V

(52)

Complete Worksheet

Resistance in Series and Parallel

(53)

Series and Parallel Circuits Summary

Series Parallel

Definition Circuit with one path for electrons to flow through

Circuit with multiple paths for electrons to flow through

Current

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54

Series and Parallel Circuits Summary

Series Parallel

Definition Circuit with one

path for electrons to flow through

Circuit with multiple paths for electrons to flow through

Current The same

everywhere in the circuit

Split up among the branches of the circuit

Voltage

(55)

Series and Parallel Circuits Summary

Series Parallel

Definition Circuit with one path for electrons to flow through

Circuit with multiple paths for electrons to flow

through Current The same

everywhere in the circuit

Split up among the branches of the circuit

Voltage Split up among the loads of the circuit

(56)

56

Power (it’s Electric!)

Power: Rate at which work is done. OR Rate

at which energy is transformed

Electric Power: The rate at which charge

(57)

Electric Power

Electric power can be calculated using the current and voltage.

Power = Current x Voltage

unit  watt, W

(58)

Complete Worksheet

Potential Difference Mixed word problems

References

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