Lesson Current And Circuits
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Battery, light bulb, and wire
"+" end
glass bulb metal end
filament plastic covering
metal side
"-" end
1
metal tip
D'Amato PTHS 2007
metal end
Inside the light bulb: a conductive path the filament is a thin metal wire
one end is connected to the metal side (an insulator separates the metal parts) the other end of the filament is connected to the metal tip 2
D'Amato PTHS 2007
What was the main message of the last slide? 1. A light bulb has metal parts connected to make a conductive path through the filament 2. A light bulb has a black plastic insulator near the base 3. The glass part of a light bulb is not a conductor 4. The filament of a light bulb is made of thin metal wire 5. A light bulb has a metal tip and metal side D'Amato PTHS 2007 3
What was the main message of the last slide? 1. A light bulb has metal parts connected to make a conductive path through the filament 2. A light bulb has a black plastic insulator near the base 3. The glass part of a light bulb is not a conductor 4. The filament of a light bulb is made of thin metal wire 5. A light bulb has a metal tip and metal side D'Amato PTHS 2007 4
Electric Current The bulb lights when there is a continuous movement of charges through the filament. A continuous flow of electric charges is called electric current There are two requirements for an electric current: 1. Separation of charges 2. A conductive path
5
D'Amato PTHS 2007
Which is the best explanation of the term "electric current"? 1) A conductive path that causes a bulb to light 2) A separation of charges that causes a bulb to light 3) A continuous flow of electric charges 4) Electrical potential energy converted into another form of energy 5) None of these is a good explanation 6
D'Amato PTHS 2007
Which is the best explanation of the term "electric current"? 1) A conductive path that causes a bulb to light 2) A separation of charges that causes a bulb to light 3) A continuous flow of electric charges 4) Electrical potential energy converted into another form of energy 5) None of these is a good explanation 7
D'Amato PTHS 2007
Separation of charges Electric potential energy exists anywhere charges are separated into areas of positive and negative. The globes of the charged Wimshurst machine have a separation of charges
8
D'Amato PTHS 2007
Which is NOT a requirement for an electric current? 1. A separation of charges 2. A filament or other thin wire 3. A conductive path 4. Paying your electric bill 5. Both 2 and 4
9
D'Amato PTHS 2007
Which is NOT a requirement for an electric current? 1. A separation of charges 2. A filament or other thin wire 3. A conductive path 4. Paying your electric bill 5. Both 2 and 4
10
D'Amato PTHS 2007
Separation of charges Separated charges will always move to reduce their separation if they can. An excess of electrons will repel each other. Electrons will be attracted to an area of net positive charge. attraction
11
D'Amato PTHS 2007
repulsion
What was the main message of the last slide? 1. Excess negative charges repel each other 2. Negative charges are attracted to positive charges 3. An explanation of why separated charges will move to reduce their separation if they can 4. Both 1 and 2 were the main message
12
D'Amato PTHS 2007
What was the main message of the last slide? 1. Excess negative charges repel each other 2. Negative charges are attracted to positive charges 3. An explanation of why separated charges will move to reduce their separation if they can 4. Both 1 and 2 were the main message
13
D'Amato PTHS 2007
Conductive path Electrons can move easily inside a conductor. Metal is the most common type of conductor. What will happen to the charges inside this conductive wire as it approaches the charged globes of the electrocope?
14
D'Amato PTHS 2007
Conductive path Electrons in the metal wire are free to move, so charges begin to separate as the wire approaches the charged globes. What happens when the wire touches the globes?
15
D'Amato PTHS 2007
Conductive path Electrons move off the wire onto the positive globe. More electrons move down the wire to balance the balance the loss. More electrons move into the wire from the positive globe. An electric current flows through the wire.
16
D'Amato PTHS 2007
In the previous slide, what will cause the electric current to stop flowing? 1. Removal of the conductive path (the wire) 2. When the net charge becomes neutral 3. When charges are no longer separated 4. Both 1 and 2 5. Both 1 and 3 6. None, the electric current will continue to flow
17
D'Amato PTHS 2007
In the previous slide, what will cause the electric current to stop flowing? 1. Removal of the conductive path (the wire) 2. When the net charge becomes neutral 3. When charges are no longer separated 4. Both 1 and 2 5. Both 1 and 3 6. None, the electric current will continue to flow
18
D'Amato PTHS 2007
Conditions for an electric current Current requires (1) a separation of charges and (2) a conductive path. If the wire is removed, the current will stop When the charges have all moved to end their separation, the current stops. That's what happens with the Wimshurst generator
19
D'Amato PTHS 2007
What was the main message of the previous slides showing charged globes and a wire? 1. Separated charges want to come together again 2. Negative charges can move along a conductive path 3. An electric current occurs when charges move 4. Both requirements for an electric current can be explained using a Wimshurst machine and some wire
20
D'Amato PTHS 2007
What was the main message of the previous slides showing charged globes and a wire? 1. Separated charges want to come together again 2. Negative charges can move along a conductive path 3. An electric current occurs when charges move 4. Both requirements for an electric current can be explained using a Wimshurst machine and some wire
21
D'Amato PTHS 2007
Separation of charges "+" end A battery also produces a separation of charges because of chemical reactions inside (When the reactive substances are all used up, the battery is dead.)
"-" end 22
D'Amato PTHS 2007
Separation of charges "+" end The chemical reactions inside the battery maintain a constant separation of charges until the battery's chemical energy is exhausted You can think of it this way: Electrons are consumed in a reaction at the + end and dumped at the ‐ end
"-" end 23
D'Amato PTHS 2007
Which of these statements about a battery is/are correct? 1. A battery contains an electric current 2. A battery provides a separation of charges 3. Chemical reactions inside the battery provide a conductive path from + end to ‐ end 4. More than one of these is correct 5. None of these is correct 24
D'Amato PTHS 2007
Which of these statements about a battery is/are correct? 1. A battery contains an electric current 2. A battery provides a separation of charges 3. Chemical reactions inside the battery provide a conductive path from + end to ‐ end 4. More than one of these is correct 5. None of these is correct 25
D'Amato PTHS 2007
An electric circuit A battery is a more common source of electric potential energy. The charges in a battery will also move through a wire if they can. If the electric charges have a conductive path to follow from negative to positive, this path is called an electric circuit.
26
D'Amato PTHS 2007
Analogy current : circuit :: 1. 2. 3. 4. 5.
27
potential : energy work : energy runners : track pipe : water chinese food : delivery man
D'Amato PTHS 2007
Analogy current : circuit :: 1. 2. 3. 4. 5.
potential : energy work : energy runners : track pipe : water chinese food : delivery man
current circulates around a circuit. runners circulate around a track.
28
D'Amato PTHS 2007
An electric circuit The charges can do useful work on their way around the circuit If they go through the filament of a light bulb, the filament will get hot enough to glow
29
D'Amato PTHS 2007
Lighting the bulb When connected correctly, electrons can move through the lightbulb across the filament. The filament is made of a material that gets hot when enough charge moves through it. It gets so hot that it glows.
30
D'Amato PTHS 2007
All the metal parts of a light bulb are conductors
But only a current that goes through the filment will light the bulb 31
D'Amato PTHS 2007
In which of these does a current flow? In which does the bulb light? A
B
C
Write down which circuits have a current Write down which circuits have a light 32
D'Amato PTHS 2007
D
In which of these does a current flow? In which does the bulb light? A
no current, no light C
B
D
no current, no light
current, no light Write down which circuits have a current Write down which circuits have a light 33
D'Amato PTHS 2007
current, light
Which has a current? Which lights? A
B
C
Write down which circuits have a current Write down which circuits have a light 34
D'Amato PTHS 2007
D
Which has a current? Which lights? A
current, light
B
C
no current, no light
current, no light
Write down which circuits have a current Write down which circuits have a light 35
D
D'Amato PTHS 2007
current, light
Elements of a circuit We draw electrical components in a simplified form to make our lives easier This is the symbol for a battery The larger line shows the + side of the battery
36
D'Amato PTHS 2007
Which diagram shows two batteries connected with one positive end touching the other negative end?
37
1.
2.
3.
4.
D'Amato PTHS 2007
Which diagram shows two batteries connected with one positive end touching the other negative end?
38
1.
2.
3.
4.
1. 2. 3. 4.
no – lines same length no – batteries not connected no – connected + to + Yes
D'Amato PTHS 2007
Elements of a circuit This is the symbol for a light bulb Wires are drawn as lines showing connections Combine the symbols to draw a circuit that contains a light bulb and a battery connected by wires
39
D'Amato PTHS 2007
Which diagram of a circuit containing a lit bulb and a battery is drawn correctly? 1.
2.
3. 4.
5. None of these is drawn correctly 40
D'Amato PTHS 2007
Which diagram of a circuit containing a lit bulb and a battery is drawn correctly? 1.
2.
3. 4.
1. no – battery wrong 2. no – connected to only one end of battery 3. no – current not through filament 4. no – battery drawn wrong
5. None of these is drawn correctly 41
D'Amato PTHS 2007
Circuit diagrams Both of these are good diagrams of a circuit that contains a light bulb and a battery connected by wires It's OK to change the position and orientation of the symbols to make the diagram clear All that matters is that you show the components connected the right way
42
D'Amato PTHS 2007
"+" end
glass bulb metal end
filament plastic covering
metal side
"-" end
1
metal tip
D'Amato PTHS 2007
metal end
Inside the light bulb: a conductive path the filament is a thin metal wire
one end is connected to the metal side (an insulator separates the metal parts) the other end of the filament is connected to the metal tip 2
D'Amato PTHS 2007
What was the main message of the last slide? 1. A light bulb has metal parts connected to make a conductive path through the filament 2. A light bulb has a black plastic insulator near the base 3. The glass part of a light bulb is not a conductor 4. The filament of a light bulb is made of thin metal wire 5. A light bulb has a metal tip and metal side D'Amato PTHS 2007 3
What was the main message of the last slide? 1. A light bulb has metal parts connected to make a conductive path through the filament 2. A light bulb has a black plastic insulator near the base 3. The glass part of a light bulb is not a conductor 4. The filament of a light bulb is made of thin metal wire 5. A light bulb has a metal tip and metal side D'Amato PTHS 2007 4
Electric Current The bulb lights when there is a continuous movement of charges through the filament. A continuous flow of electric charges is called electric current There are two requirements for an electric current: 1. Separation of charges 2. A conductive path
5
D'Amato PTHS 2007
Which is the best explanation of the term "electric current"? 1) A conductive path that causes a bulb to light 2) A separation of charges that causes a bulb to light 3) A continuous flow of electric charges 4) Electrical potential energy converted into another form of energy 5) None of these is a good explanation 6
D'Amato PTHS 2007
Which is the best explanation of the term "electric current"? 1) A conductive path that causes a bulb to light 2) A separation of charges that causes a bulb to light 3) A continuous flow of electric charges 4) Electrical potential energy converted into another form of energy 5) None of these is a good explanation 7
D'Amato PTHS 2007
Separation of charges Electric potential energy exists anywhere charges are separated into areas of positive and negative. The globes of the charged Wimshurst machine have a separation of charges
8
D'Amato PTHS 2007
Which is NOT a requirement for an electric current? 1. A separation of charges 2. A filament or other thin wire 3. A conductive path 4. Paying your electric bill 5. Both 2 and 4
9
D'Amato PTHS 2007
Which is NOT a requirement for an electric current? 1. A separation of charges 2. A filament or other thin wire 3. A conductive path 4. Paying your electric bill 5. Both 2 and 4
10
D'Amato PTHS 2007
Separation of charges Separated charges will always move to reduce their separation if they can. An excess of electrons will repel each other. Electrons will be attracted to an area of net positive charge. attraction
11
D'Amato PTHS 2007
repulsion
What was the main message of the last slide? 1. Excess negative charges repel each other 2. Negative charges are attracted to positive charges 3. An explanation of why separated charges will move to reduce their separation if they can 4. Both 1 and 2 were the main message
12
D'Amato PTHS 2007
What was the main message of the last slide? 1. Excess negative charges repel each other 2. Negative charges are attracted to positive charges 3. An explanation of why separated charges will move to reduce their separation if they can 4. Both 1 and 2 were the main message
13
D'Amato PTHS 2007
Conductive path Electrons can move easily inside a conductor. Metal is the most common type of conductor. What will happen to the charges inside this conductive wire as it approaches the charged globes of the electrocope?
14
D'Amato PTHS 2007
Conductive path Electrons in the metal wire are free to move, so charges begin to separate as the wire approaches the charged globes. What happens when the wire touches the globes?
15
D'Amato PTHS 2007
Conductive path Electrons move off the wire onto the positive globe. More electrons move down the wire to balance the balance the loss. More electrons move into the wire from the positive globe. An electric current flows through the wire.
16
D'Amato PTHS 2007
In the previous slide, what will cause the electric current to stop flowing? 1. Removal of the conductive path (the wire) 2. When the net charge becomes neutral 3. When charges are no longer separated 4. Both 1 and 2 5. Both 1 and 3 6. None, the electric current will continue to flow
17
D'Amato PTHS 2007
In the previous slide, what will cause the electric current to stop flowing? 1. Removal of the conductive path (the wire) 2. When the net charge becomes neutral 3. When charges are no longer separated 4. Both 1 and 2 5. Both 1 and 3 6. None, the electric current will continue to flow
18
D'Amato PTHS 2007
Conditions for an electric current Current requires (1) a separation of charges and (2) a conductive path. If the wire is removed, the current will stop When the charges have all moved to end their separation, the current stops. That's what happens with the Wimshurst generator
19
D'Amato PTHS 2007
What was the main message of the previous slides showing charged globes and a wire? 1. Separated charges want to come together again 2. Negative charges can move along a conductive path 3. An electric current occurs when charges move 4. Both requirements for an electric current can be explained using a Wimshurst machine and some wire
20
D'Amato PTHS 2007
What was the main message of the previous slides showing charged globes and a wire? 1. Separated charges want to come together again 2. Negative charges can move along a conductive path 3. An electric current occurs when charges move 4. Both requirements for an electric current can be explained using a Wimshurst machine and some wire
21
D'Amato PTHS 2007
Separation of charges "+" end A battery also produces a separation of charges because of chemical reactions inside (When the reactive substances are all used up, the battery is dead.)
"-" end 22
D'Amato PTHS 2007
Separation of charges "+" end The chemical reactions inside the battery maintain a constant separation of charges until the battery's chemical energy is exhausted You can think of it this way: Electrons are consumed in a reaction at the + end and dumped at the ‐ end
"-" end 23
D'Amato PTHS 2007
Which of these statements about a battery is/are correct? 1. A battery contains an electric current 2. A battery provides a separation of charges 3. Chemical reactions inside the battery provide a conductive path from + end to ‐ end 4. More than one of these is correct 5. None of these is correct 24
D'Amato PTHS 2007
Which of these statements about a battery is/are correct? 1. A battery contains an electric current 2. A battery provides a separation of charges 3. Chemical reactions inside the battery provide a conductive path from + end to ‐ end 4. More than one of these is correct 5. None of these is correct 25
D'Amato PTHS 2007
An electric circuit A battery is a more common source of electric potential energy. The charges in a battery will also move through a wire if they can. If the electric charges have a conductive path to follow from negative to positive, this path is called an electric circuit.
26
D'Amato PTHS 2007
Analogy current : circuit :: 1. 2. 3. 4. 5.
27
potential : energy work : energy runners : track pipe : water chinese food : delivery man
D'Amato PTHS 2007
Analogy current : circuit :: 1. 2. 3. 4. 5.
potential : energy work : energy runners : track pipe : water chinese food : delivery man
current circulates around a circuit. runners circulate around a track.
28
D'Amato PTHS 2007
An electric circuit The charges can do useful work on their way around the circuit If they go through the filament of a light bulb, the filament will get hot enough to glow
29
D'Amato PTHS 2007
Lighting the bulb When connected correctly, electrons can move through the lightbulb across the filament. The filament is made of a material that gets hot when enough charge moves through it. It gets so hot that it glows.
30
D'Amato PTHS 2007
All the metal parts of a light bulb are conductors
But only a current that goes through the filment will light the bulb 31
D'Amato PTHS 2007
In which of these does a current flow? In which does the bulb light? A
B
C
Write down which circuits have a current Write down which circuits have a light 32
D'Amato PTHS 2007
D
In which of these does a current flow? In which does the bulb light? A
no current, no light C
B
D
no current, no light
current, no light Write down which circuits have a current Write down which circuits have a light 33
D'Amato PTHS 2007
current, light
Which has a current? Which lights? A
B
C
Write down which circuits have a current Write down which circuits have a light 34
D'Amato PTHS 2007
D
Which has a current? Which lights? A
current, light
B
C
no current, no light
current, no light
Write down which circuits have a current Write down which circuits have a light 35
D
D'Amato PTHS 2007
current, light
Elements of a circuit We draw electrical components in a simplified form to make our lives easier This is the symbol for a battery The larger line shows the + side of the battery
36
D'Amato PTHS 2007
Which diagram shows two batteries connected with one positive end touching the other negative end?
37
1.
2.
3.
4.
D'Amato PTHS 2007
Which diagram shows two batteries connected with one positive end touching the other negative end?
38
1.
2.
3.
4.
1. 2. 3. 4.
no – lines same length no – batteries not connected no – connected + to + Yes
D'Amato PTHS 2007
Elements of a circuit This is the symbol for a light bulb Wires are drawn as lines showing connections Combine the symbols to draw a circuit that contains a light bulb and a battery connected by wires
39
D'Amato PTHS 2007
Which diagram of a circuit containing a lit bulb and a battery is drawn correctly? 1.
2.
3. 4.
5. None of these is drawn correctly 40
D'Amato PTHS 2007
Which diagram of a circuit containing a lit bulb and a battery is drawn correctly? 1.
2.
3. 4.
1. no – battery wrong 2. no – connected to only one end of battery 3. no – current not through filament 4. no – battery drawn wrong
5. None of these is drawn correctly 41
D'Amato PTHS 2007
Circuit diagrams Both of these are good diagrams of a circuit that contains a light bulb and a battery connected by wires It's OK to change the position and orientation of the symbols to make the diagram clear All that matters is that you show the components connected the right way
42
D'Amato PTHS 2007
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