Question

A CRO probe has an impedance of 500 kΩ in parallel with a capacitance of 10 pF. The probe is used to measure the voltage between P and Q as shown in the figure. The measured voltage will be?

(a) 3.53 V

(b) 3.47 V

(c) 5.54 V

(d) 7.00 V

The question was posed to me in final exam.

I need to ask this question from Miscellaneous Examples on Fourier Series topic in portion Fourier Series of Signals and Systems

Answer 1

Right answer is (b) 3.47 V

To explain I would say: \(X_C = \frac{1}{jCω} = \frac{-j}{2 × 3.14 × 100 × 10^3 × 10 × 10^{-12}}\)

Applying KCL at the node,

\(\frac{V_a-10}{100} + \frac{V_a}{100} + \frac{V_a}{500} + \frac{V_a}{-j159}\)

∴ Va = 4.37∠-15.95°.