We all know that your homes have primary voltage (V_r) 120 V that comes to them,

Question

We all know that your homes have primary voltage (V_r) 120 V that comes to them, but most doorbells only need approximately a voltage (V_s), of 10 V. This is where a transformer comes into play What type of transformer is needed to reduce the voltage? What is the turns (N) ratio? Two capacitors (C) are connected in series. The value of C_1 = 3.0 mu F and C_2 = 6.0 mu F, both are connected across a terminal of a generator that has a frequency (f) of 510 Hz. The voltage (V) in the generator is equal to 120 V What is the series equivalence of the capacitance? What is the current (I) in the circuit?

Explanation / Answer

4. (A) Step-down transformer

(B) Vp / Vs = Np / Ns

Np / Ns = 120 / 10 = 12 ( Primary to secondary coil turn ratio)

5. (A) 1/Ceq = 1/3 + 1/6

Ceq = 2 uF

(B) Z = 1 / (2 pi f C) = 1/ (2 x pi x 510 x 2 x 10^-6)

Z = 156 ohm

I = 120 / 156 = 0.77 A

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