Transcript Standard EPS Shell Presentation

Integrated Science
Unit 3, Chapter 7
Unit Three: Electricity and Magnetism
Chapter 7 Measuring Electricity
7.1
Voltage
7.2
Current
7.3
Resistance
Chapter 7 Learning Goals

Measure volts with an electrical meter.

Describe the role of a battery in a circuit.

Describe the transfer of energy in a circuit.

Explain the relationship between voltage and energy in a circuit.

Describe current as a flow of electric charge.

Measure amperes with an electrical meter.

Classify materials as conductors, semiconductors, or insulators.

Differentiate between electrical conductivity and resistance.

Explain why metals are good electrical conductors.

Measure ohms with an electrical meter.
Chapter 7 Vocabulary Terms

alternating current

ohm

ampere

resistance

battery

semiconductor

current

volt

direct current

voltage

electrical conductivity

electrical insulator

electrical conductor
7.1 Voltage
Key Question:
Why do charges move through a circuit?
*Read text section 7.1
AFTER Investigation 7.1
Measuring voltage of a cell

Set the meter to DC volts.

Touch the red (+) lead of
the meter to the (+) battery
terminal.

Touch the black (-) lead of
the meter to the (-) battery
terminal.

Adjust the meter dial as
necessary.
Measuring voltage in a circuit
 Measure
the voltage
across the battery
exactly as before.
 DO
NOT DISCONNECT
THE CIRCUIT.
NOTE: Since voltage is measured from
one point to another, we usually assign the
negative terminal of a battery to be zero
volts (0 V).
7.1 What does a battery do?

A battery uses chemical energy to move charges.

If you connect a circuit with a battery the charges
flow out of the battery carrying energy.
7.1 How do these batteries differ?

Some are smaller and don't store as much energy.

Other batteries made with Ni and Cd can be recharged.

Which battery above has the greatest voltage capacity?
7.2 Current
Key Question:
How do charges move
through a circuit?
*Read text section 7.2
AFTER Investigation 7.2
Measuring Current
 In
practical electricity,
we still label current
flowing from plus to
minus or HIGH voltage
to LOW voltage.
 Current
can't be
measured unless the
charges flow through
the meter.
7.2 Current is a flow of charge
7.2 Electricity in your house
These devices protect
you from short circuits
and fires.
7.2 Which way does
current flow?
 Either
positive or
negative charges can
flow.
 It
depends on the
materials making up the
circuit. We label circuits
from high to low current.
7.3 Resistance
Key Question:
How well does current travel through
different materials and objects?
*Read text section 7.3
AFTER Investigation 7.3
Measuring Resistance
 Set
the meter to
measure resistance (W).
 Set
the black and red
leads on opposite ends
of the objects.
7.3 Resistance

Resistance measures how difficult it is for
current to flow.
7.3 The ohm
 Resistance
is
measured in ohms
(W).

One ohm is the
resistance when a
voltage of 1 volt is
applied with a
current of 1 amp.
7.3 Why does a bulb light?

A tungsten filament has a high
resistance and glows white
when it reaches 2,500 oC.

Argon gas inside the bulb is
"inert", it doesn't chemically
react with the tungsten so it
protects it from air for use over
and over again.