Download Measuring electricity

Name_____________________________
Team__________________________
Period____
Measuring Electricity
1. Build a simple electric circuit with one dry cell and one light bulb. Use the shorter of the two bulbs given
you.
a. Measure the potential difference between the electricity going into the bulb holder and the electricity
coming out of the bulb holder, using a voltmeter. The voltmeter must be placed in parallel to the dry
cell. See the following diagram.
b. Measure the rate of flow of electricity through a circuit with an ammeter. This is called the current and
is measured in amps. The ammeter must be placed in series. See the diagram.
c. The resistance of a converter is defined as the quotient of the electric potential and the current.
Re sis tan ce (ohms ) 
Electric Potential ( volts )
Current (amps )
Calculate the resistance of the circuit.
d. The electrons leaving the light bulb have less energy than the ones entering it. Where did their energy
go?
e. The rate at which the light bulb converts energy is called its power. To calculate the power of the light
bulb, simply multiply the electric potential by the current. If the electric potential is in volts and the
current is in amps, then the power will be in watts.
Power ( watts )  Electric Potential ( volts )  Current (amps )
Calculate the power of the light bulb in the circuit.
2. Replace the taller bulb with the shorter bulb. How does the brightness of the taller bulb compare to the
brightness of the shorter one?
a. Measure the voltage of this circuit.
How does it compare to the voltage in #1?
b. Measure the current in this circuit.
How does the current compare to the current in #1?
c. In which of the two circuits do the electrons enter the bulb with more energy per electron?
How can you tell?
d. In which of the two circuits do more electrons go through each second?
How can you tell?
e. In which of the two circuits is the flow of electricity meeting greater resistance?
How can you tell?
f. In which of the two circuits is more energy being converted per second?
How can you tell?
3. What is the electric potential of the electric circuits in your home?
4. How much current is needed to light a 60 watt light bulb? Show how you came up with your answer.
5. How much current is needed to run a 600 watt toaster? Show your work.
6. How much current is needed to operate a one kilowatt hair dryer? Show your work, of course.
7. A circuit in your home can handle more than one appliance at a time. When more than one appliance is
being used on a circuit, the total current is the sum of the currents being drawn by each appliance.
a. Are the appliances wired in series or in parallel in the circuit?
b. Suppose that the toaster, your hair dryer, and several lights are all plugged into the same circuit. If the
maximum current that the circuit can handle is 15 amps, can you blow dry your hair while the toaster
and four 60 watt light bulbs are on? Explain.
c. How does a household circuit prevent you from using too much current on a single circuit?
8. Which consumes more energy, a 1200 watt microwave oven that is on for four minutes or a 60 watt light
bulb that is on for an hour? Give a complete justification of your answer.
9. Which consumes more energy, a hair dryer that is on for six minutes or a lamp that is on for 12 hours?
Give a thorough explanation of your answer.
10. Read the handout titled “Ohm’s Law and Electric Shock.”
a. Answer Question #1 from the first page of the handout. Be sure to explain how you came up with your
answer.
b. Answer Question #2 from the first page of the handout. Again, explain how you came up with your
answer.
11. Why can you get a fatal shock if you touch a downed power line, but birds can sit on power lines without
feeling a thing?
12. Most appliances in your home are grounded.
a. Why is it important that an appliance be grounded?
b. How is the grounding of an appliance done?
c. How can you tell if an appliance is grounded?