A certain wire has resistance R. Another wire, of the same material, has half th

Question

A certain wire has resistance R. Another wire, of the same material, has half the length and half the radius of the first wire. The resistance of the second wire is: R/2 R/8 R/4 2R 4R A nichrome wire is 2 m long and 3 times 10^-6 m^2 in cross-sectional area. When connected to a potential difference of 3 V, a current of 4 A exists in the wire. The resistivity of this nichrome wire is: 4.3 times 10^-8 ohm middot m 1.3 times 10^-7 ohm middot m 6.1 times 10^-7 ohm middot m 1.1 times 10^-6 ohm middot m Resistances of 4.0 ohm, 6.0 ohm, and 2.0 ohm and a 24-V emf device are all in series. The potential difference across the 4.0-ohm resistor is: 24 V 12 V 8 V 4 V

Explanation / Answer

26) R = pL/A = pL1/(pi*r1^2)

R2 = pL2/A2 = p(L1/2)(5/pir1^2)

R2 = 2R1

correct option is (d)

27) L =2 m , A =3*10^-6 m^2, V =3 V, i =4 A

from ohms law V= iR = pL/A

3 = 4*p*2/(3*10^-6)

p =1.1*10^-6 ohm.m

correct option is (d)

28) R = 4+6+2 = 12 ohm

V =iR

24 =i*12

i =2 A

in sereis combination current is constant

V = 2*4 = 8 V

Correct option is (c)

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