Question

An air-cored transformer is assumed to be 100% efficient. The ratio of the secondary turns to the primary turns is 1:20. A 240V ac supply is connected to the primary coil and a
6Ω
load is connected to the secondary coil. what is the current in the primary coil?
0.10A
0.14A
2.0A
40.0A

Answer 1

Answer on Question#55890 - Physics - Electromagnetism

An air-cored transformer is assumed to be 100% efficient. The ratio of the secondary turns $N_{S}$ to the primary turns $N_{P}$ is 1:20. A $V_{P} = 240\mathrm{V}$ ac supply is connected to the primary coil and a $R = 6\Omega$ load is connected to the secondary coil. What is the current in the primary coil?

0.10A

0.14A

2.0A

40.0A

**Solution:**

According to the ideal transformer identity

$$\frac {V _ {S}}{V _ {P}} = \frac {I _ {P}}{I _ {S}} = \frac {N _ {S}}{N _ {P}}$$

Therefore

$$V _ {S} = \frac {N _ {S}}{N _ {P}} V _ {P} = \frac {1}{2 0} 2 4 0 \mathrm {V} = 1 2 \mathrm {V}$$

The current in the primary coil is

$$I _ {S} = \frac {V _ {S}}{R} = \frac {1 2 \mathrm {V}}{6 \Omega} = 2 \mathrm {A}$$

The current in the primary coil

$$I _ {P} = \frac {N _ {S}}{N _ {P}} I _ {S} = \frac {1}{2 0} 2 \mathrm {A} = 0. 1 \mathrm {A}$$

**Answer:** 0.10A.

https://www.AssignmentExpert.com