## Monday, 3 August 2015

### ELECTRICITY RESISTANCE AND RESISTIVITY PROBLEMS

1.A wire of resistance R is bent in form of a closed circle, what is the resistance across a diameter of the circle?
2. Two wires of equal cross sectional area , one of copper and other of
Manganin have same resistance. Which one will be longer?
3. A Rectangular block of iron has dimensions L X L X b. What is the
resistance ofthe block measured between the two square ends ? Given ρ=
resistivity.
4. Three equal resistances are connected in series then in parallel. What will
be the ratio of their Resistances?
5. Two cubes A and B are of the same material. The side of B is thrice as that
of A.Find the ratio RA/RB.
6. A nichrome wire of resistivity 100X10-6ohm- m and copper wire of
resistivity1.62X10-8 ohm-m of same length and same area of cross section
are connected in series , current is passed through them, why does the

nichrome wire gets heated first?

7. A parallel combination of three resistances take a current of 7.5 A from a 30 V battery. If two
of    the resistance values are 10 Ω and 12 Ω, find the third.

8. A string of fifty 15 ohm Christmas tree lights are connected in series. One burns out, they all burn out. Calculate the total resistance.

9. A 10 ohm, 20 ohm, and 100 ohm resistors are connected in parallel. Calculate the total
resistance.