AC generator and transformer
- In an ideal transformer, the turns ratio is N_p/N_s=1/2. The ratio V_s : V_p is equal to (the symbols carry their usual meaning) : Answer: 3. 2 : 1 Key idea: For an ideal transformer V_s/V_p=N_s/N_p . Given N_p/N_s=1/2 , we get N_s/N_p=2 , so V_s:V_p=2:1 . It is a step-u... 1
- A 12 V, 60 W lamp is connected to the secondary of a step down transformer, whose primary is connected to ac mains of 220 V. Assuming the transformer to be ideal, what is the current in the primary winding? Answer: 2. 0.27 A An ideal transformer has no loss, so input power equals output power. Output power = 60 W, so V_pI_p = 60⇒ I_p=60/220≈ 0.2... 1
- A step down transformer connected to an ac mains supply of 220 V is made to operate at 11 V, 44 W lamp. Ignoring power losses in the transformer, what is the current in the primary circuit ? Answer: 1. 0.2 A Key idea: with no losses, input power = output power = 44 W. I_p=P/V_p=44/220=0.2 A. Option 1. (The secondary current is 44... 1