• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Resistance Lab. Aim - To investigate the effective resistance (total resistance) of three resistors connected in a series circuit.

Extracts from this document...

Introduction

Physics

Lab Report – Resistors in Series

  • Aim - To investigate the effective resistance (total resistance) of three resistors connected in a series circuit.
  • Background – A resistor is an electrical component which opposes the flow of current in a circuit. When a resistor is connected in a circuit it produces a voltage across its terminals (measured using a voltmeter) using this voltage and the current (measured using a milliammeter) flowing through the circuit the resistance of the resistor can be calculated. Thus Resistance = Voltage/Current, this formula has basically been derived from Ohm’s Law which states that Voltage = Current * Resistance. In this experiment we have connected three resistors with unknown resistances in series circuit, the voltage of each resistor was measured using a separate voltmeter while another one was used to measure the combined overall voltage of all three resistors, further by using the above formula we can find the individual resistance of each resistor which can be added to give the effective (total) resistance of the three resistors connected in series. This was the first process used to find the effective resistance, the second process involved using the same formula only this time the total voltage across all the three resistors was used along with the current to directly find the effective (total) resistance of the three resistors connected in series. Both the above processes were repeated with a different value of current so that an average of the effective (total) resistance of the three resistors connected in series could be calculated for each process. Thus in this way the effective resistance of three resistors connected in series was calculated and verified using two separate processes.
  • Method -    
  • Variables –

1) Controlled – The entire set of apparatus.

2) Independent – The current used.

3) Dependent – Voltage across each resistor (individual resistance) along with combined voltage of the circuit (effective resistance).

  • Apparatus – A power pack, 4 voltmeters, a milliammeter, 3 resistors and connecting wire (with crocodile clips).    
  • Diagram -  
  • Method (contd.) -    
  • Procedure –
  1. First set up the circuit shown above. In order to this connect the power pack, the ammeter and the 3 resistors in a series circuit using some connecting wire. Then connect three voltmeters across each of the three resistors and then finally connect the 4th voltmeter (Vs) across all three resistors and all three voltmeters (as shown above).
  2. Now set the current in the circuit to 150 milliamps using the power pack and the ammeter.
  3. Quickly take the readings for the voltage across each individual resistor (V1, V2 and V3) and the combined voltage across all three resistors (Vs).
  4. Now repeat the above step until you get 4 sets of readings for each value of the different voltages.
  5. Next repeat the entire above procedure using a different value of current (200 milliamps)
  6.  Now for each value of current separately calculate an average value of the voltages on V1, V2, V3 andVs.
  7. Usingthe average values of V1, V2, V3 and the value of the current calculatethe values of resistance (R1, R2 and R3) for the three resistors, with both values of current, respectively.
  8. Now add the individual values of resistance (R1, R2 and R3) for the three resistors, with both values of current, to get the value of the effective resistance.
  9. Usingthe respective value of Vs and the value of the current in both cases, calculatethe value of the effective resistance (Rs) for the entire circuit and cross check with your above answer.
  • Results –
  • Raw Data Table –
...read more.

Middle

Trial 1

Trial 2

Trial 3

Trial 4

Trial 1

Trial 2

Trial 3

Trial 4

V1 (volts)

1.2

1.4

1.3

1.2

1.8

1.6

1.7

1.8

V2 (volts)

1

0.9

0.8

0.9

1.2

1.4

1.3

1.2

V3 (volts)

3.7

3.5

3.9

3.6

5

5.1

4.8

5.1

Vs (volts)

6

6.2

5.9

6

8

8.2

8.1

8

  • Processed Data Table –

Processed Data Table showing all the values used to calculate the effective resistance of all the three resistors by both processes for both values of current along with the overall average value of effective resistance.

Current = 0.15 amps

Current = 0.2 amps

Average value of V1 (volts)

(1.2 + 1.4 + 1.3 + 1.2)/4 = 1.275

(1.8 + 1.6 + 1.7 + 1.8)/4 = 1.675

...read more.

Conclusion

I made sure that the wires would not heat up too much by keeping the circuit switched off as much as possible.I took four trials of each voltage reading for both sets of to get a more accurate average set of results.
  1. Safe Test –

In order to conduct the experiment safely, I took the following measures.

  • I handled all the apparatus carefully so that no one was hurt and so that no apparatus was damaged, the resistors were handled with special care.
  • The circuit was always kept off when not in use.
  • The work space around me was clear so that there were no accidents and so that the experimental setup was intact.
  • Evaluation –
  1. Factors that could have led to experimental inaccuracies–

The factors, which could have affected the experiment negatively thus causing any experimental inaccuracies, are given below.

  • A slight error while measuring the volatges could have led to anomalies.
  • The current flowing through the circuit could have been slightly more or less than required, thus leading to inaccurate results.
  • While keeping the circuit on for too long the wire could have heated up thus affecting the resistances in the circuit.

...read more.

This student written piece of work is one of many that can be found in our International Baccalaureate Physics section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related International Baccalaureate Physics essays

  1. Marked by a teacher

    Experiment to calculate the diameter of a piece of nichrome wire from its electrical ...

    3 star(s)

    length is directly proportional to the resistance as the trendline is linear. [KD5]From graph 1, the average gradient was found and from graph 2, the uncertainty of the average gradient was determined. The gradient can then be substituted into the equation and rearranged to find the diameter.

  2. IB Specific Heat Capacity Lab

    (6) - (7) (see data table) (T3 - T2) = 78.50 - 26.50 = 52.00 oC � (0.25 + 0.25) = � 0.50 oC = (0.50 � 52.00) � 100 = 0.96 % Heat absorbed by water (Hw) MW � CW � ?T = 61.47 � 4.18 � 4.50 = 1156.25 J = (0.03 + 11.11)%

  1. IB Physics Lab - Resistance

    * I also believe that when more resistors are added in a circuit, either series or parallel, the percent error will increase. Materials * Resistors * Breadboard * Multimeter Procedure 1. First, we obtained several different resistors, a breadboard, and a multimeter.

  2. Factors affecting an electromagnet

    Since the Magnetic field around the nail increases, its ability to attract more paperclips will also increase and so when these two factors do increase then the number of paperclips attracted to the nail will also increase". Since the instructor has provided a hypothesis, it is the students turn to

  1. Testing ohms law on a light bulb and a resistor connected to a source ...

    17.07�3 65.01�3 262�3 19.60�3 75.2�3 260�3 19.99�3 76.9�3 260�3 Graph 1.2 voltage versus current for a resistor Table 1.2 the current and resistance of a resistor when the voltage is varied.

  2. Investigating resistors

    Turn power supply on and find potential difference and current 3. Record results in table 4. Add second resistor in series with the first. Measure the current and total potential difference and compare the results 5. Then 3rd resistor in series with the first two 6.

  1. HL Physics Revision Notes

    Entropy The Second Law of Thermodynamics implies that thermal energy cannot spontaneously transfer from a region of low temperature to a region of high temperature Entropy is a system property that expresses the degree of disorder in the system The entropy of the universe can never decrease.

  2. How does the sinkage depth of a tyre affect its rolling resistance ?

    Multiple samples of each tire /size are tested to establish an average rolling resistance value. The rolling resistance in a tire typically declines moderately as the tire temperature rise from cold to normal operating conditions during the first 30 minutes of driving every time the vehicle is used.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work