1. 20.2 Electric Current and Ohm’s Law
Key Concepts
What causes an electric current?
What are some examples of conductors
and insulators?
What factors affect electrical resistance?
How are voltage, current, and resistance
related?

2. If one part isn’t functioning, the flashlight _______ light
The different parts of a flashlight form a continuous path for through which charges can __________
If one part isn’t functioning, the flashlight _______ light
flow
won’t
Flow of current
Switch
Negative terminals
Spring
Positive terminals

3. The continuous flow of electric charge is an electric ___________
The SI unit of electric current is the ampere _____, or _______, which equals 1 coulomb per second ______
current
(A)
C/s
amp
Flow of current
Switch
Negative terminals
Spring
Positive terminals

4. In direct current ______, charge flows in only ________ direction.
A flashlight and most other battery-operated devices use direct current.
In alternating current ______, a flow of electric charge regularly _______________ its direction.
Electric current in your home and school is mostly alternating current.
(DC)
one
(AC)
reverses

5. Conductors and Insulators
____________such as copper and silver are good electrical ________________.
A material through which charge can flow
_____________.
Wood, plastic, rubber, and air are good electrical ________________.
A material through which charge ___________
flow easily.
Metals
conductors
easily
insulators
cannot

6. Conductors and Insulators
A metal wire is usually _____________ with plastic or rubber. .
The coating around a wire helps to _____________ the current and keep it where it is needed.
coated
control

7. Resistance is _________________ to the flow of charges in a material.
As electrons move through a conducting wire, they _______________ with electrons and ions.
These collisions convert some kinetic energy into _____________ energy, and the current is ________________.
The SI unit of resistance is the _______(Ω)
opposition
collide
thermal
reduced
ohm

8. Resistance
A material’s _______________, ____________, and _________________ affect its resistance.
Resistance is ____________ in a longer wire because the charges travel ___________.
As temperature increases, a metal’s resistance increases because electrons collide more ______________.
thickness
length
temperature
greater
farther
often

9. Using a thick straw to drink a milkshake is _____________ than using a thin straw.
Similarly, electrons flow more easily through a ___________ wire than they flow through a thin wire of the same material.
easier
thick
metal ions
electron

10. Recall that potential energy is related to _____________.
Voltage
In order for charge to flow in a conducting wire, the wire must be connected in a complete ___________ that includes a _____________ of electrical energy.
Recall that potential energy is related to _____________.
The potential energy of a charge depends on its
position in an electric ____________.
loop
source
position
field

11. Voltage
Potential difference is the difference in electrical potential energy between _______ _______________ in an electric field.
Potential difference is measured in joules per coulomb, or ____________.
Because it is measured in volts, potential difference is also called __________________.
two
places
volts
voltage

12. Three common voltage sources are…. __________________
A source of voltage does _________ to increase the potential energy of electric charges.
Three common voltage sources are….
__________________
work
batteries
solar cells
generators

13. Batteries, like other voltage sources, have _________________ that can
A battery is a device that converts _____________ energy into ______________ energy
Batteries, like other voltage sources,
have _________________ that can
connect to ________ in a circuit
A voltage ________, or potential
difference, is maintained across
the terminals
chemical
electrical
terminals
wires
drop

14. Increasing the voltage ____________ the current.
Ohm’s Law
Increasing the voltage ____________ the current.
Keeping the same voltage and increasing the resistance ________________ the current.
increases
decreases

15. Ohm’s Law
According to Ohm’s law, the voltage (____) in a circuit equals the product of the current (____) and the resistance (______). V I R

16. Ohm’s Law
What is the voltage if the resistance is 3 ohms and the current is 3 amps?
V =
3 amps
x 3 ohms
= 9 volts

17. Ohm’s Law
A ________________ can be used to measure current, voltage, or resistance.
multimeter

18. Assessment Questions
1. If a piece of wire has a certain resistance, which wire made of the same material will have a lower resistance?
a hotter wire
a thicker wire
a longer wire
a thinner wire

19. Assessment Questions
2. What does the voltage between two points in an electric field represent?
the total kinetic energy
the difference in mechanical energy
the difference in potential energy
the electrical energy

20. Assessment Questions
3. A 9-volt battery drives an electric current through a circuit with 4-ohm resistance. What is the electric current running through the circuit?
0.44 A
2.25 A
5 A
36 A

21. Assessment Questions
4. The two types of electric current are direct current and indirect current. True False