Transformer Equation Quiz with Answers: Current and Turns Ratio

📚 Quick Study Guide

• ⚡️ A transformer changes AC voltage from one level to another.
• 🔄 The core principle is mutual induction between two or more coils.
• 🔢 Turns Ratio: $N_p / N_s$, where $N_p$ is the number of turns in the primary coil and $N_s$ is the number of turns in the secondary coil.
• 💡 Voltage Ratio: $V_p / V_s = N_p / N_s$, where $V_p$ is the primary voltage and $V_s$ is the secondary voltage.
• 🔌 Current Ratio: $I_p / I_s = N_s / N_p$, where $I_p$ is the primary current and $I_s$ is the secondary current.
• 🎯 Power in an ideal transformer: $V_p * I_p = V_s * I_s$
• ✍️ Remember that in a step-up transformer, voltage increases ($V_s > V_p$) and current decreases ($I_s < I_p$). Conversely, in a step-down transformer, voltage decreases ($V_s < V_p$) and current increases ($I_s > I_p$).

🧪 Practice Quiz

1. Question 1: A transformer has 500 turns on its primary coil and 100 turns on its secondary coil. If the primary voltage is 240V, what is the secondary voltage?
1. A) 1200V
2. B) 48V
3. C) 240V
4. D) 12V
2. Question 2: A transformer steps up the voltage from 25V to 250V. If the secondary coil has 1000 turns, how many turns does the primary coil have?
1. A) 10000
2. B) 100
3. C) 10
4. D) 1000
3. Question 3: If the current in the primary coil of a transformer is 5A and the turns ratio (Np/Ns) is 4, what is the current in the secondary coil?
1. A) 20A
2. B) 1.25A
3. C) 5A
4. D) 4A
4. Question 4: A transformer has a primary voltage of 120V and a secondary voltage of 12V. What is the turns ratio (Np/Ns)?
1. A) 1/10
2. B) 10
3. C) 1
4. D) 12
5. Question 5: In a transformer, if the primary current is 2A and the secondary current is 10A, what is the ratio of secondary turns to primary turns (Ns/Np)?
1. A) 5
2. B) 0.2
3. C) 2
4. D) 10
6. Question 6: A transformer with 400 primary turns and 100 secondary turns is connected to a 200V AC source. What is the voltage across the secondary coil?
1. A) 50V
2. B) 800V
3. C) 200V
4. D) 40V
7. Question 7: If the turns ratio (Np/Ns) of a transformer is 0.5 and the primary current is 8A, what is the secondary current?
1. A) 4A
2. B) 16A
3. C) 8A
4. D) 0.25A