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Quick Advice/Suggestions for ISC Physics Practical 2017

According to the new marks distribution the Marks Breakdown is as follows:

• Practical Questions : 15 marks
• Project Work : 10 marks
• Practical File : 5 marks

Practical Questions are based on two types:

1. Optical Experiment
2. Electrical Experiment

So, the following combinations are possible:

1. Optical : 6 marks + Electrical : 9 marks (Chances of a question based on graph)
2. Optical : 9 marks (Chances of a question based on graph) + Electrical : 6 marks

For Optical:

Practice determination of focal length using :

• u – v method
• displacement method

For Electrical:

• Practice determination of the potential gradient of the wire through which steady current flows.
• Determination of the e.m.f. of a dry cell

Note : For steady current, we either don’t use a resistance box in the experiment or we don’t change the value of resistance in the resistance box. In such type of experiment, for different lengths of the wire i.e. 20 cm, 30 cm etc, you measure the potential difference using voltmeter and then plot a graph of Potential difference vs length. Find the slope which is the potential gradient of the wire.

Points to note while performing experiment:

• Ensure ‘tip to tip’ parallax removal.
• Ensure that you follow the given circuit diagram while making the circuit.
• Ensure that the DC Source is set to the voltage mentioned in the question.
• Do not keep the circuit switched ON for too long. Either switch of the DC source or remove the key.
• The polarity (i.e. positive/negative terminals) of the apparatus may not be marked in the diagram. So, ensure that your connection follows proper polarities. (e.g. if you have connected the ammeter to the circuit using a particular polarity and after switching on the circuit, the current reading shows below 0 A, then interchange the connection on the terminals of ammeter.)
• While finding null point suing a galvanometer, make sure that the deflection on the galvanometer is on either side when touching the 2 ends of the given meter bridge/scale.

Points to note while recording readings:

• Note down the least count of the instruments like voltmeter with proper units before starting the experiment.
• Record all observations up to appropriate number of decimal places depending on the least count of the measuring instrument.

(e.g. If L.C of Voltmeter = 0.05 V, the reading recorded should be 2.20 V and not 2.2 V. Similarly, for lengths, all readings should have 1 decimal place i.e. 20.0 cm instead of 20 cm)

• When using the galvanometer to find the null point length, express it up to 1 decimal place (e.g. write 68.0 cm instead of 68 cm)
• The value of a quantity or any observation must always be supported with correct units.
• Pay attention to statements like “answer correct upto 2 decimal places” or ” 4 significant figures“ and follow the instruction.
• Do not overwrite and manipulate your result.
• While doing any optical experiment with lens, always record the positions of object pin, image pin and the lens.
• Record the observations neatly, in a tabular form, with proper heading and with units as per the instructions.
• Do not waste time by writing unnecessary information which is not asked like procedure, theory, diagram.

Points to note while plotting graph:

• 1st variable must be plotted on the Y axis. (e.g. if graph is ‘m’ vs ‘v’, then ‘m’ should be along the Y axis and ‘v’ along the X axis)
• Label the axes correctly with units.
• Choose uniform and convenient scale such that at least 2/3 of the graph paper is used.
• Mention the scale used in the graph clearly.
• DO NOT use KINK* along any axis. Instead shift the origin.
(*Kink is a zig-zag sign near the origin that shows that the scale interval started there, just that the numbers after it were skipped)
• Plot the points correctly [thin (.) encircled points (blob (●) is a miss plot)]
• Draw the best fit line passing through most points.
• Line should be thin and uniform covering extreme plots.
• Untouched points should be close and equally distributed on either side of the line.
• While finding slope, take two un-plotted points (i.e. not from the readings) on the best-fit line and separated from each other through a distance of more than 50% of the line drawn.
• Express slope up to the given significant figures/decimal point.
• Origin should begin from zero if the intercept is to be found.
• Co-ordinates of the origin must be given/ marked on graph paper.
• Express the final result with proper units.

I hope that the students will find this to be useful.

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ISC 2017 Physics Theory Solution + Examiner’s Comments – From the Council

Solution of ISC 2017 Physics Theory (Paper 1) as provided by the Council for the Indian School Certificate Examinations.

1. We cannot use KINK at all?
Marks are sure to be deducted?

2. In plotting the graph do we have to mark both the coordinates beneath each plotted point eg (0,0) for origin and (20,02) for a point say…

3. Sir, according to some rumours there is a small viva conducted too. Is it true and if yes how to prepare for it

4. Using KINK along the axes results in deduction of marks ?

5. If the deflection in the galvanometer doesn’t come at different sides at the two ends of the wire , what should we try changing ?

• Do the following :
1) Check the positive and negative connections of the galvanometer. Normally Jockey is connected to negative terminal of galvanometer.
2) Check positive and negative connections of dry cell.

6. Sir…while finding null point in galvanometer..what if the galvanometer shows deflection only in one direction…what is the reason..is that galvanometer defective or there’s defect in my circuit?

• Do the following :
1) Check the positive and negative connections of the galvanometer. Normally Jockey is connected to negative terminal of galvanometer.
2) Check positive and negative connections of dry cell.

7. are this enough to secure good marks in isc 2017 physics practicals