A step-down electrical transformer operates on a 2200 V primary line and delivers power at 220 V to a 22-ohm load. Assuming an ideal 100 percent efficient transformer, what is the primary current?
Answer and explanation
Correct answer: C. 1.0 A
- Step 1: Secondary current: I_s = V_s / R = 220 V / 22 ohms = 10.0 A. Step 2. Transformer power balance: V_p I_p = V_s I_s. Step 3. I_p = (V_s / V_p) I_s = (220 / 2200) 10.0 = (1/10) 10.0 = 1.0 A. Answer: 1.0 A. Why not the others:* 10.0 A is the secondary current; 0.10 A squares the turns ratio.
Practise more Electromagnetism and Wave Optics.
Free questions with an explanation for every one, and full timed ECAT Pakistan mock tests.
More Electromagnetism and Wave Optics questions
- A copper rod of length L = 0.50 m moves at constant speed v = 4.0 m/s perpendicular to a uniform magnetic field B = 0.60 T. What motional el…
- In an RLC series circuit at resonance frequency f_0, what is the phase difference between the supply voltage and the circuit current?
- What is the resonant frequency of an LC circuit consisting of an inductor L = 2.0 mH and a capacitor C = 5.0 microfarads?
- Unpolarized light of intensity I_0 passes sequentially through two ideal polarizers whose transmission axes are oriented at an angle of 60 d…
- What is the energy stored in a 10.0 microfarad capacitor charged to a potential difference of 200 V?
- Which Maxwell equation expresses the empirical physical fact that magnetic monopoles do not exist in nature?