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Grade 10General Physics

8. A piece of wire having resistance R is cut into four equal parts. (i) How will the resistance of each part compare with the original resistance? (ii) If the four parts are placed in parallel, how will the resistance of the combination compare with the resistance of the original wire?9. Why is a bird perched on a high voltage wire not killed by the current?10. How many 176Ω resistors (in parallel) are required to carry a current of 5A in 220V line?11. 100J of heat are produced each second in a 4Ω resistance. Find the p.d. across the resistor.12. A polythene piece rubbed with wool is found to have negative charge of 3 × 10 -7 C. Estimate the number of electrons transferred.

Question image for 8. A piece of wire having resistance R is cut into

Sourabhsaroj

10 Years agoGrade 10

1 Answer

Vikas TU

10 Years ago

Dear Souarabh,

(i) After cutting the wires in four parts the cross section area x length donot remain constant to orignal length.

Therfore here R we use would be diectly prop. to the square of its length.

Hence, R = kl^2..................(1)

after cutting,

r = k (l/4)^2..........................(2)

Divide both eqns.

R/r = 16

r = R/16

thus each resistance value would be R/16

Since now u know the values of each resistance U can now do next questios easily.

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