# What is the current flowing through the wires?

1. Oct 30, 2015

### songminho

1. The problem statement, all variables and given/known data
A power plant produces energy at a voltage of V = 15435 V. Before being sent along long distance power lines this electricity is sent through a transformer with 112 turns in the primary coil and 8613 turns in the secondary coil. If the wires have an efficiency of 99.60 percent and a resistance of 1323 ohms, what current flows through these wires?

2. Relevant equations
V = IR
V1/V2 = n1/n2

3. The attempt at a solution
V1/V2 = n1/n2
15435/V2 = 112/8613
V2 = 1186979.063

V = IR
I = V / R
= 1186979.063 / 1323
= 897.1875 A x 99.6%
= 893.5988A

2. Oct 31, 2015

### rude man

Weird wording. There is no load specified, ergo not possible to compute current. And I never heard of wire "efficiency".
Maybe the load is supposed to be 1323 ohms and the wire power loss 0.4%?

3. Oct 31, 2015

### Staff: Mentor

The above is treating the 1323 Ohms as a load resistance (dividing the transmitted voltage by 1323 Ohms) which is not correct, as 1323 Ohms was given to be the power line resistance. There must be some other unspecified load at the end of the transmission line.

Perhaps the OP's course text provides a definition for efficiency of a power distribution system? For example, if it represents the percentage of the transmitted power delivered at the load end of the transmission line.

Such a definition would tell us something about the ratio of VR to VT in the above diagram...