Question

To the Y input of a CRO, we feed a signal defined by 10sin100t, to the X-input, we feed signal 10cos100t. The gain for both X channel and Y channel is the same, the screen will show?

(a) Sinusoidal signal

(b) A straight line

(c) An ellipse

(d) A circle

The question was posed to me in an international level competition.

My query is from Advanced Problems on CRT and CRO in portion Oscilloscopes of Electrical Measurements

Answer 1

Correct answer is (d) A circle

For explanation: The pattern observed on the CRT, when two sinusoidal signals are applied to the X-X and Y-Y plates of the CRT are known as Lissajous pattern.

sin φ = \(\frac{y_1}{y_2} = \frac{X_1}{X_2}\)

∴ Screen will show a circle.