Title: Electricity, Circuits, Voltage and Batteries 17.1
1Electricity,Circuits, Voltage and Batteries17.1
2Objectives
- Define electric current.
- Identify the electric symbols for basic circuit
elements. - Use a multimeter to test continuity.
- Identify and construct open, closed, and short
circuits. - Define voltage source.
- Distinguish between parallel and series
arrangements of batteries. - Construct electric circuits with batteries
connected in series and in parallel. - Calculate the combined voltage of batteries
connected in series and in parallel.
3Physics terms
- electric current
- ampere (A)
- electric circuit
- open circuit
- closed circuit
- short circuit
- voltage
- volt (V)
- battery
- voltmeter
4What is electricity?
Electricity is the flow of electric charges,
typically through wires, conductors, and
electrical devices. Sometimes we can see the
effects of electricity in nature.
5What is electric current?
Electric current is the flow of charged
particles, usually through wires and circuits.
Current is measured in amperes (A), also called
amps.
Animated illustration, page 472
6How do we measure electric current?
Electric current is measured using an ammeter or,
more commonly, a digital multimeter.
7What is an electric circuit?
An electric circuit is a conducting path through
which electric current can flow. The symbol for
electric current is I.
In this circuit, I 0.3 amps.
8Charge is conserved
I
Electric current I must be the same at all points
in a simple, single-loop circuit. Charge can
never be created or destroyed. All the charge
that flows through one point in the circuit must
flow through the next point also.
I
9Open and closed circuits
An open circuit does not have a complete path so
no current flows.
A closed circuit has a complete path, allowing
current to flow.
10Common circuit elements
11Knife blade switches
A knife blade switch uses a mechanical lever to
open/close a circuit connection.
12What is a short circuit?
13Assessment
- Which statement below is a correct definition of
electric current? Electric current is . . . - the energy of moving electrical charges.
- the flow of electric charges through a wire or
circuit. - the number of electrons in a circuit element.
- the attraction between charged particles in a
wire.
14Assessment
- Label each of these electrical symbols with the
name of the electrical component it represents
battery resistor lamp switch or wire.
15Assessment
- Identify the following circuits
16A reliable source of current
- Prior to 1800, no one knew how to create a steady
supply of electric current. - Alessandro Volta was the first to succeed.
- He discovered that placing two different metals
in an acid or salt solution produced an electric
current between the terminals. - He connected multiple voltaic piles together to
create a battery of them.
Adolphe Ganot, Elementary Treatise on Physics,
1893
17What is a battery?
- A battery is a device that converts stored
chemical energy into electrical energy. - Batteries come in many different kinds even
lemons!
electrical energy
chemical energy
18Reading a battery
Batteries come in many sizes and voltages 1.5,
6, 9, 12 V, for example. Voltage is the electric
potential difference between the two terminals of
a battery. Voltage is measured in volts (V),
named after Volta, the inventor of the battery.
19How is voltage measured?
Voltage is measured using a voltmeter or a
digital multimeter.
20Volts and amps
Current and voltage are the two most important
physical quantities for understanding electric
circuits.
- Current measures the flow of charge through a
wire. - Voltage measures the change in electrical
potential energy per unit of charge.
21A useful analogy
- Charges in a wire are analogous to water in a
pipe - Electric current is analogous to the flow of the
water. - The battery is analogous to the water pump.
- Voltage is analogous to the change in
gravitational Ep.
22What is a series connection?
In a series connection, the batteries are
connected one after the other. The positive
terminal of one battery is connected to the
negative terminal of the next battery.
23What is a parallel connection?
In a parallel connection, the same ends of both
batteries are connected together.
24Batteries in Series or Parallel
- To calculate the voltage across batteries
connected in series or in parallel - When batteries are connected in series, the
voltages add together. - When identical batteries are connected in
parallel, the total voltage remains the same.
25Why does it work this way?
When these batteries are connected in
series, the voltages add together.
Electric charge (1 coulomb) passing through a 1.5
volt battery gains 1.5 joules of Ep. Passing
through a second 1.5 volt battery gains another
1.5 joules of Ep.
Its like climbing a stairway to the second
floor, then another stairway to the third floor.
26Why does it work that way?
When these batteries are connected in parallel,
the total voltage remains the same.
Electric charge passes through one battery OR the
other. It ONLY gains 1.5 joules of Ep because
each charge ONLY passes through one battery.
Its like climbing either of two stairways from
the first to second floor.
27Assessment
- Which statement below provides a correct
practical definition of a voltage source? A
voltage source . . .
- creates an electric potential difference between
two points in a circuit, such as the two ends of
a battery. - provides the electrical potential energy needed
for a circuit to operate. - is analogous to the pump in a system of
circulating water. - all of the above.
28Assessment
- Identify which circuit has batteries connected in
series and which has batteries in parallel.
29Assessment
- Calculate the voltage across the batteries for
each circuit.
30Assessment
- What does the 1.5 V label on the battery mean?
- The voltage of the positive terminal is 1.5 V.
- The voltage of the negative terminal is 0 V.
- The voltage between the positive and negative
terminals is 1.5 V. - All of the above