What is the reflected impedance in the primary of the transformer circuit shown?
- 20 ohms
- 500 ohms
- 50 ohms
Explanation from PART66Online
A transformer reflects the load into the primary multiplied by the square of the turns ratio: Zp = (Np / Ns) squared x Zs = 10 squared x 5 = 100 x 5 = 500 ohms. The ratio is squared because the primary voltage is 10 times the secondary voltage while the primary current is one tenth of the secondary current, and impedance is voltage divided by current. The 50 ohm option multiplies by the ratio only once, and 20 ohms divides the squared ratio by the load (100 / 5).
T
tijaku asked · 5 Jun 2013
? should be 50 ohms !
Community Comments (1)
P
PART66Online
6 Jun 2013
No.
Turn ration = square_root(impedance ratio), so impedance ratio = 10^2 = 100
Hence impedance is 5 * 100 = 500
Turn ration = square_root(impedance ratio), so impedance ratio = 10^2 = 100
Hence impedance is 5 * 100 = 500
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