Transcript Potential difference and power (4.2)

4.2 Potential difference ( pd ) and power
Potential Difference:
* is defined as the work done (or energy transfer) per unit charge
V (Volt)
=
W
Q
(work done, J)
(charge, C)
+
B
If 1J of work is done in moving 1 C
of positive charge from A to B then the
Pd is 1V
A
+
1V = 1 J / C
4.2 Potential difference ( pd ) and power
Potential Difference:
* is defined as the work done (or energy transfer) per unit charge
V (Volt)
=
W
Q
(work done, J)
(charge, C)
+
B
If 1J of work is done in moving 1 C
of positive charge from A to B then the
Pd is 1V
A
+
1V = 1 J / C
4.2 Potential difference ( pd ) and power
Potential Difference:
* is defined as the work done (or energy transfer) per unit charge
V (Volt)
=
W
Q
(work done, J)
(charge, C)
+
B
If 1J of work is done in moving 1 C
of positive charge from A to B then the
Pd is 1V
A
+
1V = 1 J / C
4.2 Potential difference ( pd ) and power
Potential Difference:
* is defined as the work done (or energy transfer) per unit charge
V (Volt)
=
W
Q
(work done, J)
(charge, C)
+
B
If 1J of work is done in moving 1 C
of positive charge from A to B then the
Pd is 1V
A
+
1V = 1 J / C
4.2 Potential difference ( pd ) and power
Potential Difference:
* is defined as the work done (or energy transfer) per unit charge
V (Volt)
=
W
Q
(work done, J)
(charge, C)
+
B
If 1J of work is done in moving 1 C
of positive charge from A to B then the
Pd is 1V
A
+
1V = 1 J / C
Voltage or pd:
* is electrical pressure
* causes current to flow
* is measured in Volts (V)
with a voltmeter in parallel
1.5 V
1.5 V
V
1.5 V
1.5 V
1.5 V
1.5 V
1.5 V
Voltage or pd:
* is electrical pressure
* causes current to flow
* is measured in Volts (V)
with a voltmeter in parallel
1.5 V
1.5 V
V
1.5 V
1.5 V
1.5 V
1.5 V
1.5 V
Voltage or pd:
* is electrical pressure
* causes current to flow
* is measured in Volts (V)
with a voltmeter in parallel
1.5 V
1.5 V
V
1.5 V
1.5 V
1.5 V
1.5 V
1.5 V
Voltages in series circuits
Energy
from a
battery
The cell gives electrical potential energy
to each electron – even when not connected
e……..
-
JJJ
J
E……..
w….
e…….
* Work is done by an electron when passing through a component.
* Some of the electron’s electrical potential energy is transferred to heat and light.
* The work done per coulomb of charge is called the potential difference across
the component
Voltages in series circuits
Energy
from a
battery
The cell gives electrical potential energy
to each electron – even when not connected
e……..
-
JJJ
J
E……..
w….
e…….
* Work is done by an electron when passing through a component.
* Some of the electron’s electrical potential energy is transferred to heat and light.
* The work done per coulomb of charge is called the potential difference across
the component
Voltages in series circuits
Energy
from a
battery
The cell gives electrical potential energy
to each electron – even when not connected
e……..
-
JJJ
J
E……..
w….
e…….
* Work is done by an electron when passing through a component.
* Some of the electron’s electrical potential energy is transferred to heat and light.
* The work done per coulomb of charge is called the potential difference across
the component
Voltages in series circuits
V
Energy
from a
battery
e……..
E……..
w….
e…….
V
V
Voltages in series circuits
1.5 V
V
Energy
from a
battery
e……..
E……..
w….
e…….
V
V
3 V
4
3 V
4
The higher the v……... of the battery the more energy
the electrons can t………... to the bulbs.
The bulb f………. heats up.
Some of this heat energy is transformed to l…... energy.
voltage
transfer
filament
light
Voltages in series circuits
V
V
V
Voltages in series circuits
3.0 V
V
V
V
1.5 V
1.5 V
In a series circuit
the voltage is shared
across components
Voltages in series circuits
3.0 V
V
1.5 V
1.5 V
V
V
A
0.2 A
In a series circuit
the voltage is shared
across components
Voltages in series circuits
V
3.0 V
V
A
V
V
V
0.1 A
In a series circuit
the voltage is shared
across components
Voltages in series circuits
3.0 V
3 V
4
3 V
4
V
V
A
V
V
V
3 V
4
3 V
4
0.1 A
In a series circuit
the voltage is shared
across components
Voltages in series circuits
3.0 V
3 V
4
3 V
4
V
V
A
V
Each bulb adds more
resistance to the
series circuit.
The current flowing drops.
The voltage across
each bulb drops
V
V
3 V
4
3 V
4
0.1 A
In a series circuit
the voltage is shared
across components
4.2 Potential difference ( pd ) and power
Problem:
If 30 J of work is done when 5C of charge passes through a component,
calculate the potential difference across the component.
V (Volt)
=
V
=
W
Q
30 J
5C
=
(work done, J)
(charge, C)
6V
4.2 Potential difference ( pd ) and power
Problem:
If 30 J of work is done when 5C of charge passes through a component,
calculate the potential difference across the component.
V (Volt)
=
V
=
W
Q
30 J
5C
=
(work done, J)
(charge, C)
6V
4.2 Potential difference ( pd ) and power
EMF
Electromotive force of a source of electricity:
* is defined as the electrical energy produced per
unit charge passing through the source
W ( J)
Electrical energy
produced when charge Q
moves through the source
=
(Volt) X
Q ( C)
For a component with
For a component with
For a component with
For a component with
For a component with
For a component with
For a component with