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1. ### How many 0.25-pF capacitors must be connected in parallel in order to store 1.2µC of charge when connected to?

Q = C*V C = Q/V = (1.2*10^-6/10) = 1.2*10^-7 Capacitors in parallel add, so if we need n capacitors C = 1.2*10^-7 = n*0.25*10^-12 n = 1.2*10^-7/(0.25*10^-12) = 4.8*10^5 = 480,000 <<<

1 Answers · Science & Mathematics · 11/02/2014

2. ### What is the power factor in a direct short circuit?

Depending on what device and how it was shorted. For pure resistance load shorts, PF = 1 Other partial short on transformer, it is no more equal to one.

2 Answers · Science & Mathematics · 31/01/2014

3. ### Question on ac power?

...factor = cos 17.17' = .956 (C) Power dissipated = (VA)*(pf) = (230V)*(7.45A)*(.955) = 1636.4 Watts Power ...

1 Answers · Science & Mathematics · 20/01/2014

4. ### A few electricity questions?

1. D both B & C ; since 3300 pF = 3300E-12 F = 3.3E-9 F = 3.3nF = 0.0033 ...

2 Answers · Science & Mathematics · 14/01/2014

5. ### in practical transformers does Isc equal I full load and how ?

...for series R and X: |Z| = V * I with a phase angle PF (Power factor) = true_watts / apparent_VA = cos(θ) θ = ...

2 Answers · Science & Mathematics · 18/01/2014

6. ### how does the efficiency of a transformer vary with the power factor of the load?

More than anything else the efficiency is dependent on load. Most transformers are designed to reach maximum efficiency at 75 to 80% full load, dropping slightly toward full load and ever more steeply as load is reduced. Here I understand...

2 Answers · Science & Mathematics · 13/01/2014

7. ### Phase Locked loop with 3 IC's?

... [kΩ] 3K R2 [kΩ] 300K C1 [pF] 680 pF FREQ.MIN [kHz] 877 VTUN = 1.1...

2 Answers · Science & Mathematics · 16/01/2014

8. ### how to calculate one month power factor while we know KWh & KVARh only?

...the same for both the kWh and kVARh, then the power factor would be: PF = Cos(ATan(1500/5000)) = 0.96 or 96% You have to recognize that...

2 Answers · Science & Mathematics · 17/01/2014

9. ### What is this little electrical component in RC Car?

It's a ceramic capacitor. Value appears to be 47 nF or 47000 pF. It is probably used to suppress spikes from the motor.

1 Answers · Science & Mathematics · 11/01/2014

10. ### Power in an ac circuit....where am I going wrong?

... Also: (V^2)/(Z) = VA But (VA)*(pf) = power pf = cos arc tan XL/R = cos [arc tan (28.27/60)] = .905 Z...

5 Answers · Science & Mathematics · 05/01/2014