CBSE Guess > Papers > Important Questions > Class X > 2008 > Science > Science By :- Nagesh Kumar

Science - Electricity

1. What is electric current?
2. What is the SI unit of electric current?
3. What is the SI unit of electric charge?
4. What is ohm’s law? Give its mathematical expression?
5. How much current will an electric heater coil draw from a 220 volt line, if the resistance of the heater coil is 40? 
6. Calculate the number of electrons constituting one coulomb of charge.
7. The potential difference between the terminals of an electric heater is 30 volt when it draws current of 4 A from the source. What current will the heater draw if the potential difference is increased to 120 volt?
8. A current of 4 A exists in a 10  resistor for 4 minute. Find the charge and the number of electrons that pass through any cross-section of the resistor in this time
9. Why are metals able to conduct electricity
10. How should the resistances be connected so that the equivalent resistance is increased?
11. The combination of resistances shown below has equivalent resistance equal to 12 ohm, what is the value of R?  



12. Which metal is the best conductor of electricity at room temperature?
13. Calculate the amount of charge that would flow in 1 hour through the elements of an electric bulb drawing a current of 0.4 A.
14. What is the power of an electric lamp, if it draws 20 A current when connected to 220 V line?
15. To produce 1000 joule of heat in 10 seconds, how much voltage should be applied to 50  resistance.
16. In the circuit diagram given below, find the equivalent resistances and total current flowing through the circuit.
17. a) State the law, which relates the current in a conductor to the potential difference across its ends.
    1. Draw the V-I graphs for a
    2. A simple electric circuit has 24 V batteries and a resistor of 30 ohm. What will be the current in the circuit?
18. What is a magnet?
19. What is the SI unit of induced current?
20. What is the frequency of d.c current?
21. What is the principle on which working of electric generator is based? What are their important parts?
22. Why two magnetic lines of forces don’t intersect each other?
23. Give two methods with which we can increase the strength of magnetic field produced by a circular coil carrying current?
24. State the following laws:
1. Maxwell’s right hand rule.
2. Fleming’s left hand rule
3. Fleming’s right hand rule.
25. What do you mean by electromagnetic Induction? Explain the induction of current in the secondary coil with change in current in primary coil.
26. Distinguish between an electric motor and generator?
27. What are the factors which govern the force experienced by a current carrying conductor placed in a uniform magnetic field depends?
28. What is the frequency of a.c current that you use in your house?
29. What is magnetic field?
30. There is a battery operated toy, what kind of motor is being used in it?
31. Give two example of devices in which d.c motor is used.
32. Give two examples in which a.c motor is used.
33. What will be the frequency of an alternating current, if its direction changes after every 0.05 sec?
34. What is direct current (d.c) and alternating current (a.c).
35. What is the principle behind the working of electric generator? Explain its working with the help of well labeled diagram.