A standard coil marked 3W is found to have a true resistance of 3.115 W at 300 K. Calculatge the temperature at which marking is correct. Temperature coefficient of resistance of the material of the coil is `4.2 xx 10^(-300C^(-1)`.
Text Solution
Verified by Experts
The correct Answer is:
`290.2K`
`t = 300 K = 300- 273 = 27^(@)C` `R_(27) = R_(0)(1+ alpha xx 27)` `R_(27) = R_(0)(1+ alpha xx 27)`……(i) `:. 3.115 = R_(0) (1+ 4.3 xx 10^(-3) xx27)` ....(i) and `3 = R_(0)(1+ 4.2 xx 10^(-3) xx t)`…..(ii) `:. (3)/(3.115) = (1 + 4.2 xx 10^(-3) xx t)/(1+ 4.2 xx 10^(-3) xx 27)` On solving we get `t = 17.21^(@)C` `= 17.21 xx 275 = 290.2K`
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Knowledge Check
The resistance of a wire at room temperature 30^@C is found to be 10 Om now to increase the resistance by 10% the temperature of the wire must be [the temperature coefficient of resistance of the material of the wire is 0.002 per @C ]
A
`36^@C`
B
`83^@C`
C
`63^@C`
D
`33^@C`
The resistance of a wire at room temperature 30^@C is found to be 10 Om now to increase the resistance by 10% the temperature of the wire must be [the temperature coefficient of resistance of the material of the wire is 0.002 per @C ]
A
`36^@C`
B
`83^@C`
C
`63^@C`
D
`33^@C`
A wire has a resistance of 3.1 Omega at 30°C and a resistance 4.5 Omega at 100°C. The temperature coefficient of resistance of the wire
A
`0.008^(@) C^(-1)`
B
`0.0034^(@) C^(-1)`
C
`0.0025^(@) C^(-1)`
D
`0.0012^(@) C^(-1)`
PRADEEP-CURRENT ELECTRICITY-Problems for Practice (A)
