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# Daily Archives: September 20, 2011

## Download the newly included portion by CBSE for CLASS 12 Physics

CBSE has added some content for class XII. This includes mainly portions from “Combination of mirrors and lenses

XII Class Supplementary Study Material

## A few selected questions fro CBSE Class 10 Physics Summative Assessment 1

Dear students,

If you are preparing for the CBSE Summative Assessment I for Class X, Give the following questions a try.

If you are not able to solve any of it, please post your doubts as comments to this post. The questions can be discussed here with due explanations.

Make it a practice to solve as much Sample papers and Guess papers as you can before writing the Board Exam.

All the best

1. An electric geyser has the ratings 2000W, 220V marked on it. What should be the minimum rating in whole number of a fuse wire, that may be required for safe use with this geyser? (1Marks)
2. Consider a circular loop of wire lying in the plane of a table. Let the current pass through the loop clockwise. Draw the direction of magnetic field inside and outside the loop. (2Marks)
3. A wire is stretched so as to make its length double. What is the effect on its resistivity and why? (2Marks)
4. Define electric power. Write its SI unit. What is the value of 1 kWh in joules. (2Marks)
5. A torch bulb is rated 3.0V, and 600mA. Calculate its (i) power (ii) resistance (iii) energy consumed if this bulb is lighted for 4 hours.  (3Marks)
6. (i) Differentiate between AC and DC giving two points of difference. (ii) What is the frequency of AC and DC in India? (iii) Draw a graph of current – time for AC and DC. (3Marks)
7. Name and state the law which relates the potential difference in a circuit to the magnitude of current that flows through it. Give its mathematical expression and draw the theoretical graph too. (3Marks)
8. What is electromagnetic induction? State Fleming’s Right Hand Rule. A coil of copper wire is connected to a galvanometer. What would happen if a bar magnet is (a) pushed into the coil with north pole entering first? (b) pulled out of the bar magnet? (c) held stationary inside the coil?
9. State Joule’s law of heating. How does the electric fuse prevent fires due to shortcircuit or overloading? A household uses the following electric appliances. (i) Refrigerator of rating 400W for ten hours each day. (ii) two electric fans of rating 80W each for twelve hours each day. (iii) six electric tubes of rating 18W each for six hours each day. Calculate the electricity bill of the household for the month of June if the cost per unit of electric energy is Rs. 3.00. (5Marks)

## Numerical from Motion and Force for CBSE Class 9 SA1

A steam engine of mass 30000 kg pulls 2 wagons each of mass 20000 kg with an acceleration of 0.2 m/s/s. neglecting frictional force calculate (i) the force exerted by the engine (ii) the force experienced by each wagon

(Srija posted)

In this case the engine is pulling the rest of the wagons.

The force exerted by the engine = total mass of the wagons x acceleration = 2 x 20000 x 0.2 = 8000 N

Each wagon experiences a net force = 20000 x 0.2 = 4000 N

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