Q. 1. Name a device that helps to maintain the potential difference across a conductor
Q. 2. Why ammeter is connected in series whereas voltameter is connected in parallel through a circuit?
Q. 3. Name the material used as filament in heater and electric bulb.
Q. 4. The p.d. between the terminals of an electric heater is 60v when it draws a current of 4A from a source.What current will the heater draw if p.d is increased to 120v.
Q. 5. What are difference between resistivity and resistance?
Q. 6. If resistance of a device kept constant and p.d decreases to half , what will be effect on its current?
Q. 7. Why are coils of heating appliances are made of alloys rather than metals?
Q. 8. What is variable resistance?
Q. 9. Why rheostat is used?
Q. 10. R1 , R2 & R3 are three resisters connected in series . derive equivalent resistance for circuit. If value of two resistance are 10 ohm and 20ohm , and a current of 5A flow through circuit having p.d 12v , find value of third resistor if all 3 are connected in parallel
Q. 11. What are advantages of connecting electrical device in parallelwith the batteries instead of series?
Q. 12. State joule’ s law. An electric iron consumes energy at rate of 840w when heating is at maximum rate and 360 w when heating is at minimum.The voltage is 220v . what are the current and resistant in each case?
Q. 13. Why inert gas such as nitrogen , filled in electric filament?
Q. 14. What is fuse? What type of material should be used for it?Give the rating of fuse for a device marked as 1000w –220v.
Q. 15. What is commercial unit of electrical energy? Express it in joule.
Q. 16. For resistors of equal values are connected through p.d 220v and carry current of 5A . Find values of each resistors.
Q. 17. Why we should not connect a bulb and a heater in series ?
Q. 18. What is electric power? Give its SI unit.
Q. 19. Why aluminium and copper wires generally used for transmission of current?
Q. 20. Why high tension wires are used for long distance transmission?
Q. 21. Why does a compass needle get deflected when brought near bar magnet?
Q. 22. Define magnetic field lines . what is direction of magnetic field lines inside magnet?
Q. 23. How the relative strength of magnet is expressed?
