149 problem 4 copper has resistivity of pc 172 10 8 q m an extension cord made of copper is conn

Step 1: Recall the formula for resistance, which is given by R = ρ * (L/A), where ρ is the resis

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Problem 4: Copper has a resistivity of Pc = 1.72 x 10^-8 Ω-m. An extension cord made of copper is connected to a DC electric motor which requires a current of at least Imin = 75A in order to operate. The cord is connected to a V = 115V source. Part (a) Input an expression for the maximum ratio of length to cross-sectional area the cord can have if the motor is to operate. Part (b) What is the ratio numerically in [m^-1]? Part (c) Experimentally, it is found that the maximum length the cord can be is Lmax = 30m. What is the wire's minimum diameter, Dmin, in meters?

          Problem 4: Copper has a resistivity of Pc = 1.72 x 10^-8 Ω-m. An extension cord made of copper is connected to a DC electric motor which requires a current of at least Imin = 75A in order to operate. The cord is connected to a V = 115V source.

Part (a) Input an expression for the maximum ratio of length to cross-sectional area the cord can have if the motor is to operate.

Part (b) What is the ratio numerically in [m^-1]?

Part (c) Experimentally, it is found that the maximum length the cord can be is Lmax = 30m. What is the wire's minimum diameter, Dmin, in meters?

Added by Anne H.

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