answers to review guide 2013
7th Grade Science ­ Circuits Test
Review Packet: Answer Key
Circuits Test: Lesson 5­9
Science 7
1. Draw a schematic of an open series circuit with one light and one fan. Make your power source be a compound battery with 2 batteries in parallel. answers to review guide 2013
7th Grade Science ­ Circuits Test
2. How could you make the light brighter and the fan faster in the circuit above? Explain your reasoning and draw a schematic.
3. How would you define a master switch in a circuit? (hint: how is it different than a regular switch?) ­A master switch opens/breaks the path to all circuits or in the circuit that all devices are in ­This will turn all devices on or off. ­The master switch is in series with the batteries or the power source. If it is open/up, then none of the electrical energy is allowed through.
Added 4. Circle or label the master switch in each Later
circuit below:
answers to review guide 2013
7th Grade Science ­ Circuits Test
5. How is a series circuit different than a parallel circuit?
Series Circuit:
circuit with only ONE closed path connecting components to the electrical power source.
1
Parallel Circuit: circuit with MORE THAN ONE closed path connecting components to the power source. devices can work independent or separate from one another.
1
or
1
2
2
6. How are devices connected in series different than devices connected in parallel?
Devices connected in­series rely upon/depend upon the other devices to work/function. If one of the devices or the power source are not connected, then all devices in­
series will be off/not function.
Devices in­parallel do not rely/depend upon one another. Each device(es) function independently of one another and do rely upon each other to function/receive energy from the power source.
in­series
in­series
l
lle
ra
pa
­
in
l
le
al
ar
­p
in
rie
se
in­
s
answers to review guide 2013
7th Grade Science ­ Circuits Test
7. What is a compound battery?
A compound battery is 2 or more batteries connected together. The batteries can be connected in­series, in­
parallel, or a combination.
8. Draw three different examples of compound batteries: 2 Batteries 2 Batteries 3 Batteries
in series in parallel in series
9. Use the schematic below as a starting point.
a.Redraw the schematic in the box provided with the following added­
i.Add a voltmeter that will be able to show the voltage on the battery
ii.Add an ammeter to show the current in the circuit iii.Add a fan in parallel to the light bulb
answers to review guide 2013
7th Grade Science ­ Circuits Test
10.Write the meter reading for the meter that has the question mark.
A1 = 0.6A
A2 = _______?
A3 = 0.3A
10.
answers to review guide 2013
7th Grade Science ­ Circuits Test
11. Which way does electricity flow out of a battery? Explain why using the schematic
All electricity flows from negative to positive. This occurs because only the negatives (electrons) can move from one object/material to another. However, the only reason the electrons leave the battery is to follow the conducting path to the positive (protons) side of the battery. Electrons (negative) are attracted / pulled towards the Protons (positive).
Electrons flowing clockwise (in green)
Fan Spinning
(in orange)
11. How is the fan rotation affected if you switch the wires on the fan? ­The fan will spin one way when the wires are hooked to the fan as shown to start. If the wires are switched on the battery or on the fan, then the fan will spin the other way, because the electrons are entering from the other side of the fan now. ­The reason is that electrons only flow in one direction ­ From the Negative end to the Positive end of the battery.
How are the lights affected?
­The lights will function the same either way the wires are connected. The only thing the lights require is a complete/closed circuit for the electrons to flow through.
flow of electrons (green)
flow of electrons (green)
fan spining (orange)
fan spining (orange)
answers to review guide 2013
7th Grade Science ­ Circuits Test
12. What does an ammeter measure?
­An ammeter measures electrical current. ­This is the amount/quantity of/how many electrons flowing through the circuit each second. ­Your ammeter measures mA (milliamperes).
­The ammeter is always in the path (hooked in­series) of the electrons. The current flows through the ammeter.
What does a voltmeter measure?
­A voltmeter measures voltage.
­Voltmeters are always connected in­parallel to the devices/power sources they are measuring.
­Voltage is the force that the electrons are moving with.
­When a battery is fully charged it has its highest voltage (maxmimum negatives opposite positives) The greate the imbalance of electrons and protons, the greater the force the electrons have as they move.
correct hook up of a voltmeter
­Electricity continues to flow
­All lightbulbs will be on.
­Voltmeter will show a reading
incorrect hook up of a voltmeter
­Electricity stopped at this point
­none of the lightbulbs will be on.
­Voltmeter will show a reading
answers to review guide 2013
7th Grade Science ­ Circuits Test
14.For each of the following write on the line if the circuit below is a series or parallel circuit:
parallel
series
series
parallel
15. For each of the following schematics under the table, label in the table below if the indicated lights are on or off. Put an X in the box for each of your answers.
L1
ON
Off
L2
L3
L4
answers to review guide 2013
7th Grade Science ­ Circuits Test
16. Draw the schematic for the following compound batteries. highest voltage reading.
Circle which compound battery would have the 2 Batteries in series 2 Batteries in parallel
3 Batteries in series 3 Batteries in parallel
17. What are the advantages and disadvantages of compound batteries in series vs parallel?
Batteries in parallel: Voltage and mA remain the same with addition of each battery
Advantage:
­lasts longer, because less energy is used. Only the equivalent of one battery is used at one time.
­if one battery dies (runs out of energy) it will still provide energy from the other batteries left.
Disadvantage:
­less energy given off. Lights will be dim and fans will spin slowly. Batteries in series: Voltage and mA will increaese with addition of each battery.
Advantage:
­will provide energy from all batteries. Fans will spin fast and light bulbs will be bright.
Disadvantage: ­Energy will last a short amount of time because the energy is given out/use at a faster rate.
­If one of the batteries in series dies (runs out of energy) no more power will be provided = The circuit will not receive any energy.
answers to review guide 2013
7th Grade Science ­ Circuits Test
18. & 19. Directions: Draw a circuit with two batteries, three light bulbs, and two switches so that it has all the following components:A
A. master switch that turns the entire circuit on or off. (controls everything)
B. One light bulbs remains lit when the other light bulb is taken out of its light socket/turned off.
C. A switch that will turn 1 light bulb on or off at the same time, but will keep the other light not affect the other.
A.
C.
B.
20. Answer the following questions about the circuit you built:
A. Are the light bulbs connected in series or parallel? How can you tell?
­One light bulb ins connected in one loop with its own switch.
­The other light bulb is in its own loop.
­The two loops independent/separate of one another. Meaning that one
light turns on and off, no matter if the other light is on or off.
B. Are the batteries and the master switch in series or parallel? How can you tell?
­The master switch is in­series with the batteries. This is shown by the fact that when the master switch is open, it breaks/opens the entire circuit.
­Even if all other devices and switches are connected in the correct/on position, the master switch will either allow all energy to the circuit or not. ­Both loops are supplied energy from the batteries, only when the switch is closed/down.