Download Ohm`s Law and Basic Circuit Theory – Answer Sheet

Ohm’s Law and Basic Circuit Theory – Answer Sheet
Ohm’s Law:
Q1) On your worksheet sketch the circuit. Set the resistance to 140 ohms. Complete
the table on your worksheet. As you increase the voltage the number of batteries will
increase in 1.5-volt increments. Note hat the simulation shows current flow not
electron flow. Current flows from positive to negative and the electrons flow from
negative to positive. Current flow is an historical aberration. There is no physical
material flowing as is shown for the current. What is really occurring is an electron
flow. Nevertheless current flow is still spoken of.
Place sketch here:
Resistance (Ohms)
140
140
140
140
140
140
Voltage (Volts)
1.5
3.0
4.5
6.0
7.5
9.0
Current (milliamps)
Q2) Complete the following statement; as the voltage across the resistor is doubled
the current that flows through the resistor is ...
Q3) What did you notice about the physical size of the V and the I in the equation as
this increase in voltage occurred
Q4) What therefore can be said about the relationship between current and voltage
given a constant resistance value in the circuit as shown?
Q5) Using the data from the table above open an Excel spreadsheet and copy the data
for voltage and current into the spreadsheet. Plot the voltage on the y-axis and the
current on the x-axis. Make sure you use a scatter plot. Add a trend line to the graph
that is plotted and make sure that you display the equation of the line on the graph.
Q6) What is the equation of this line and what is its significance?
Q7) Set the voltage to 4.5 volts and change the resistance in increments of 100 ohms.
Remember that the voltage that is supplied by the batteries is then applied across the
resistor. Complete the following table.
Voltage (volts)
4.5
4.5
4.5
4.5
4.5
4.5
4.5
4.5
4.5
4.5
Resistance (Ohms)
100
200
300
400
500
600
700
800
900
1000
Current (mA)
Q8) What conclusion can be drawn regarding the current that flows in a circuit as the
resistance is increased with constant voltage applied. Be specific with your answer.
Q9) The equation for Ohm’s Law can be written in three different forms each with a
different quantity as the subject of the equation. Write each of these in the space
provided.
Q10) Write a word statement summarising Ohm’s Law by completing the following
statement:
The current that flows through a resistor in a circuit is .......
Circuit Theory:
a) Using Voltmeters and Ammeters:
Q11) What values are displayed on the voltmeter and the ammeter? Remember
voltmeters measure energy difference of the electrons between two points and
ammeters measure current or electron flow.
Q12) The voltmeter placed as it was is essentially part of the circuit. Electrons must
therefore pass through the voltmeter. What conclusion can be drawn about placing
voltmeters in circuits in this fashion with respect to the circuit’s ability to allow
electron flow?
Attach the voltage probes to positions A and B. Close the switch. Click the Show
Values dialog box. Record the values in the table.
Device
Measurement (add appropriate units
for each measurement)
Ammeter
Light Globe
Voltmeter
Battery
Switch
Q13) The battery increases the energy of the electrons. Given that 1-volt represents
an energy gain of 1 joule per coulomb what energy gain does this battery supply?
Q14) The light bulb uses the energy of the electrons. What energy loss does the light
bulb produce in the electrons?
Q15) The resistance of the switch is stated as zero ohms. Connect the voltmeter
across the switch. How much energy is lost per coulomb of electrons as they pass
through the switch.
Q16) Determine the current flowing through the light bulb by using the appropriate
form of the Ohm’s Law equation. How does the value that you calculated compare to
the value as shown on the simulation?
Q17) Measure the voltage across the each light globe and then across the two light
globes. Record the values in the table.
Voltage
Voltage across A only
Voltage across B only
Voltage across AB
Q18) Summarise the results above.
Q19) The brightness of the bulb is shown by yellow lines surrounding it. Compare
the brightness of the bulb(s) when the circuit has one bulb and when it has two bulbs.