Chapter 20 Assessment
Ms. Basualdo
VOCABULARY
Section 20.1
1. Coulomb 2. electrically neutral 3. positive
4.negative 5. static electricity 6. charged
Section 20.2
7. electric current
8. switch
circuit
10. resistor
9. closed
11. electric circuit 12. Electricity
circuit
13. open
Section 20.3
14. Ampere 15. battery 16. voltage 17. multimeter 18. Volt
Section 20.4
19. Ohm 20. Ohm's law
21. conductor
22.resistance
23. insulator
24. Semiconductor 25. potentiometer
Concepts
Section 20.1
1. repel, attract
2. An object with a net charge of zero is said to be electrically neutral.
3. If it loses electrons, its net charge is positive.
4. Because ordinary matter has zero net (total) charge, most matter
acts as if there is no electric charge at all.
5. The unit of charge is the coulomb. The name was chosen in honor of
Charles Augustin de Coulomb (1736–1806), the French physicist
who performed the first accurate measurements of the force
between charges.
6. In the drying process, some kinds of fabrics lose charge and some
gain charge. Static cling occurs between fabrics that have opposite
charges. Two items of clothes of the same kind of fabric usually
don't stick together; however, two items of different fabrics might.
For example, a cotton sock might stick to a pair of nylon running
shorts.
Section 20.2
7. a Circuit 2 is closed.
b. Circuits 1 (no bulb), 3 (there is no bulb), 4 (circuit is open,
bulb won’t light)
c. 1 is open because there is no bulb in the socket; 3 and 4 are
open because the switch is open
8. When drawing a circuit diagram, symbols are used to
represent each part of the circuit. These electrical
symbols make drawing circuits quicker and easier than
drawing realistic pictures.
Section 20.3
10. Current is what actually flows and does work. A difference in voltage
provides the energy that causes current to flow.
11. A battery is like a water pump because the battery supplies electrical
potential energy to a circuit and a pump provides potential energy to
water.
12. Multimeters can measure both voltage and current for AC and DC while
ammeters measure only current and voltmeters only voltage (potential
difference).
13. a. Set the multimeter to measure DC voltage. Close the circuit. Place
the
probes across the bulb with one on each side and read the display.
b. Set the multimeter to measure DC current. Break the circuit on one side
of the bulb. Re-connect the circuit with the probes (the bulb will light).
Read the display.
14. To protect the multimeter, always be sure you break the circuit and use
the meter to re-connect the circuit. Always be sure there is a resistor of
some kind in the circuit so you don't overload the multimeter with too
much current. Never measure current in a short circuit with the
multimeter.
Section 20.4
15. If the resistance is doubled, the current will be reduced to
half (1/2) the product of the current in a circuit and the
resistance in the circuit is a constant.
16. The current in a circuit is dependent upon the voltage.
Doubling the voltage in a circuit doubles the current.
17. voltage, resistance
18. a. The current will decrease.
b. More current will flow in the circuit.
19. Copper is a very good conductor. The covering
material acts an insulator to the wire from
making contact with objects that should not be
exposed to the current and voltage of the
conducting copper wire.
Section 20.1
1. a. repel
b. Attract
c. repel
Problems