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Potential Difference

Pawan Asked

“What is meant by potential difference?”


“Potential Difference between two points is the difference in Potential between the two points and is equal to the work done per unit charge ion carrying a positive test charge from one point to another against the electric field and without any acceleration”

It is correct to say the weight of the body is 10 kg?

It is correct to say the weight of the body is 10 kg? (Khalid asked)


As such it is not correct. But, kg. wt (kilogram weight) is the unit of weight and therefore someone simply says kg instead og kgwt hoping that it is understood that what they mean is kgwt.

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)

The SI & CGS unit of time is same .Why?

Almost in all systems of unit second is the unit of time, most probably because, second is the most convenient one, if we look at the guidelines for selecting a unit.

For more details refer to the following links

  1. http://www.aticourses.com/international_system_units.htm
  2. http://www.french-metrology.com/en/history/history-mesurement.asp
  3. http://physics.nist.gov/cuu/Units/history.html
  4. http://en.wikipedia.org/wiki/Metric_system
  5. http://en.wikipedia.org/wiki/Systems_of_measurement

Difference between g and G

What is the difference between capital ‘G’ and small ‘g’ in the chapter gravitation?

 g  G
 Acceleration due to gravity  Universal constant of gravitation
 varies from place to place  A constant everywhere on earth
 vector quantity  A dimensional constant
 unit is ms-2  unit is Nm2kg-2

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