CURRENT ELECRICITY
1 mark questions
1. Why manganin is used for making standard resistor?
2. The sequence of bands marked on a carbon resistor are: Red, Red, Red, Silver. Write the value of resistance with tolerance.
3. A wire of resistivity ρ is stretched to three times its initial length, what will be its new resistivity.
4. If p.d.v applied across a conductor is increased to 2v, how will the draft velocity of the electrons change?
5. A 10Ω thick wire is stretched so that its length becomes three times. Assuming that there is no change in its density on stretching. Calculate the resistance of new wire.
6. Give any two applications super conductors.
7. Two wire of equal length one copper and manganin have same resistance , which wire is thicker?.
8. A copper wire of resistivity r is stretched to reduce its diameter to half of its previous value .What will be the new resistances?
OR
A wire of resistance 4R is bend in the form of circle .What is the effective resistance between the ends of diameter?.
2 marks questions
9. You are given 8 Ω resistor. What length of wire of resistance 120 Ωm-1 should be joined in parallel with it to get a value of 6 Ω ?
10. Three resistance 3Ω,6Ω and 9Ω are connected to a battery. In which of them will the power dissipation be maximum if
a) They all are connected in parallel
b) They all are connected in series Give reason.
11. A silver wire has a resistance of 2.1Ω at 27.5˚c and a resistance of 2.7Ω at 100˚c. Determine the temperature coeff. of resistivity of silver.
12. The variation of potential difference with length in case of two potentiometres A and B is given below.Which of the two is more sensitive.
13. If the length of the wire conductor is doubled by stretching it , keeping potential difference constant by what factor the drift speed of the electron changes.
14. Two 120V light bulbs , one of 25W and another of 200W are connected in series . One bulb burnt out almost instantaneously ?.Which one was burnt and why?.
15. A cylindrical metallic wire is stretched to increase its length by 5% . Calculate the Percentage change in resistances.
16. A wire of resistance 4R is bend in the form of circle .What is the effective resistance between the ends of diameter?.
17. Two wires A and B have same lengths and same material, have their cross sectional areas 1:4 , what would be the ratio of heat produced in these wires when the voltage across each is constant.
18. Two bulbs whose resistance are in the ratio of 1:2 are connected in parallel to a source of constant voltage. What will be the ratio of power dissipation in these?
OR
Plot of current I versus time interval is given below. Find the charge that flows through the wire during this time period 
3 Marks Question
19. A student has two wire of iron and copper of equal length and diameter.He first joins two wires in series and pass electric current through the combination which increases gradually.After that he joins two wires in parallel and repeats the process of passing current.Which wire will glow first in each case?
20. Total resistance of the circuit is R/3 in which three identical resistors are connected in parallel. Find the value of each resistance?.
21. Amount of charge passing through the cross section of a wire is q(t)=at2+bt+c.Write the dimensional formula for a, b and c. If the values of a, b and c in SI unit are 6, 4, 2 respectively. Find the value of current at t=6 seconds.
22. Prove that current density of a matellic conductor is directly-proportional to the speed of electrons.
23. Name the carriers of electric current in
1) a bar made of silver
2) hydrogen discharge tube
3) a germanium semiconductor
4) a wire made of alloy nichrome
5) supper conductor.
6) salt water
24. a potential difference V is applied across the ends of length I and diameter D .what is the effect on drift velocity of electrons if
a) V is doubled
b) I is doubled
c)D is doubled
25. Draw a graph showing variation of resistivity with temperature for
a) nichrome
b)silicon
26. A uniform wire of resistance “R” is shaped into a regular “n” sided polygon,
where “n” is even. Find the equivalent resistance between
1) opposite corners of the polygon
2) adjacent corners of the polygon.
27. Under what condition is the heat produced in an electric circuit
1) directly proportional
2) inversely proportional to the resistance of the circuit?
5 Marks Questions
28. state the working principle of potentiometer explain with the help of circuit diagram how the emf of two primary cells are compared by using the potentiometer
29. State Kirchhoff’s law an electrical network. Using the Kirchhoff’s laws deduce the condition for balance in the Wheat-stone bridge.
30.State the working principle of potentiometer explain with the help of circuit diagram how the potentiometer is used to determine the internal resistance of the given primary cell.
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