Question

lug-in transformer supplies 9.00 V to a video game system. (a) How many turns are in its secondary coil if its input voltage is 120 V and the primary coil has 384 turns? 1742 Incorrect: Your answer is incorrect. How are the number of turns in the secondary and primary coils related to the input and output voltages? turns (b) What is its input current when its output is 1.14 A?

Answer 1

Answer:

-29turns

- NsVp = NpVs

- 0.086A

Explanation:

Using the transformer formula that relates the number of turns N of the coil, the emf V in the coils and the current I generated in the coil as shown;

Ns/Np = Vs/Vp = Ip/Is where;

Ns and Np are the number of turns in the secondary and primary coil respectively

Vs and Vp are the emf in the secondary and primary coil respectively

Is and Ip are the current in the secondary and primary coil respectively

Given Np = 384turns, Vp = 120V (input voltage) Vs = 9V (output voltage) Ns =?

From the formula Ns/Np = Vs/Vp

Ns/384 = 9/120

Cross multiplying

120Ns = 384×9

120Ns = 3456

Ns = 3456/120

Ns = 28.8

Ns = 29turns approximately

- The relationship between the number of turns in both coils to their voltages is as expressed;

Ns/Np = Vs/Vp

NsVp = NpVs

- The input current is the current in the primary coil while the output current is the current in the secondary coil. According the expression earlier given;

Vs/Vp = Ip/Is

Given Vs = 9V, Vp = 120V, Is = 1.14A Ip= ?

Substituting the data into the formula to get the current in thee primary coil which is the input current we have;

9/120 = Ip/1.14

Cross multiplying;

120Ip = 9×1.14

120Ip = 10.26

Ip = 10.26/120

Ip = 0.086A

Answer 2

Answer:

(a) Ns = 28.8 turns.

( relationship) NsVp = VsNp

(b) Ip = 0.0855 A

Explanation:

(a)

Using

Ns/Np = Vs/Vp................. Equation 1

Where Ns = Number of turns in the secondary coil, Np = Number of turns in the primary coil, Vs = Voltage in the secondary coil, Vp = Voltage in the primary coil.

Make Ns the subject of the equation

Ns = Np(Vs/Vp).................... Equation 2

Given: Np = 384, Vs = 9 V, Vp = 120 V

Substitute into equation 2

Ns = 384(9/120)

Ns = 28.8 turns.

The ratio of the number of turns in the secondary coil to the the number of turns in the primary coil = The ratio of the number of the secondary voltage to the primary voltage.

Ns/Np = Vs/Vp

NsVp = VsNp ( relationship)

(b)

Using,

Ns/Np = Ip/Is..................... Equation 3

Where Ip = Input current, Is = output current

make Ip the subject of the equation

Ip = Is(Ns/Np)...................... Equation 4

Given: Is = 1.14 A, Ns = 28.8 turns, Np = 384 turns

Substitute into equation 4

Ip = 1.14(28.8/384)

Ip = 0.0855 A