NAME: ……………………………………… CLASS ………….. DATE: ………………

PRACTICAL NO.: ……

An investigation into Ohm’s Law relationship and the determination of theresistance of an unknown resistor.

AIMS:

1. To investigate the relationship between the potential difference across a resistor and the current in the resistor.

2. To determine the resistance of the unknown resistor.3. To obtain accurate measurements.4. To record the information obtained in both tabular and graphical form.5. To analyse and interpret information.

INSTRUCTIONS:

1. Pay careful attention during the pre-prac talk and take notes so that you are sure what you must do when you carry out the investigation.

2. Decide on and write up an action plan to investigate the relationship between the current in and the potential difference across the resistor given to you, and to determine its resistance.

3. Choose the appropriate apparatus.4. Use the apparatus and take the necessary measurements to obtain the data required – at

least three sets of readings should be taken.5. Present the data in a tabular form and as a graph.6. Use the data to establish Ohm’s Law and to determine the resistance of the resistor.

PROCEDURE:

1. Describe your action plan, including the statement of the problem, the apparatus needed, the method that you will follow and a circuit diagram.

2. Carry out your investigation, setting up the apparatus that you have chosen, and taking the necessary measurements and readings.

3. Record your results in a suitable table and represent these results on a graph.4. Interpret your results in terms of Aims 1 and 2.5. How would the results be affected if the resistor became hot?

ASSESSMENT:

Consult the rubrics on the next page that will be used to assess your work. Ensure that you have attempted to satisfy all the requirements. The total number of marks allocated to the practical is indicated on the rubric sheet.

NAME: ………………………………………….. CLASS: ………. DATE: ………………

Assessment of Ohm’s law practical

Assessment of investigative and manipulative skills:

CRITERIA Competency levelNot achieved

1Partially achieved

2Achieved

3States the problem 1 2 3Presents action plan 1 2 3Presents list of apparatus and a circuit diagram

1 2 3

Chooses correct apparatus 1 2 3Uses apparatus correctly 1 2 3Is accurate in taking measurements 1 2 3

(18)

Assessment of recording skills

CRITERIA Competency levelNot achieved

1Partially achieved 2

Achieved3

Collects data 1 2 3

Sorts data 1 2 3

Completes a table correctly 1 2 3

Presents results correctly in a graph 1 2 3

(12)

Assessment of interpretation of data and drawing conclusions

CRITERIA Competency levelNot achieved

1Partially achieved

2Achieved

3Able to define Ohm’s law 1 2 3

Identifies relationship between V & I 1 2 3

States conclusions to investigation 1 2 3

Discusses reasons for any deviations 1 2 3

(9)

Maximum marks: 42 Mark achieved:………..

Sample results for the Ohm’s law experiment:

1. When the reading on the voltmeter connected across the unknown resistor was 2 V, the current in the circuit was found to be 1 A.

2. When the voltmeter reading changed to 3 V, it was noted that the current in the circuit changed to 1.5 A.

3. When the voltmeter reading changed to 4 V, it was noted that the current in the circuit changed to 2 A.

4. When the voltmeter reading increased to 5 V, it was noticed the current in the circuit increased to 2.5 A.

5. Tabulate your results and determine the resistance of the unknown resistor.

6. Draw a graph to illustrate the relationship between V and I for the resistor.

7. Using the graph, derive the Ohm’s law definition if you can.

6 V

A R

V