Question

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4. Complete these sentences using while. Follow the model.

Model: The ammeter is used to measure the value of current....

The ammeter is used to measure the value of current while the ohmmeter is used to measure the value of resistance.

1. The ohmmeter is used to measure the value of resistance...........

2. The ammeter is connected in series...

3. When the ammeter is used to measure the value of current the circuit should be opened



5. Pair work. Put these questions to your groupmate. Let him/her answer
them.

1.What is the ammeter used for?

2. What is the voltmeter used for?

3. What is the ohmmeter used for?

4. What terminals does a meter have?

5. Should the measured circuit be opened when the voltmeter is used?

6. Should the measured circuit be opened when the ammeter is used?

7. In what way should the voltmeter be connected to the circuit?

8. In what way should the ammeter be connected to the circuit?

9. What is the difference between a voltmeter and an ammeter?

10. What common meters are used to measure the values in a circuit?



6. Solve the following problems:

1. Suppose the ammeter scale reads 1.9 amp, the voltmeter scale reads 2.4 V; how much is the value of resistance in the measured circuit?

2. Suppose the ohmmeter scale reads 75 ohms, the voltmeter scale reads 220 V; how much is the value of current in the measured circuit?

3. Suppose that you have a series circuit consisting of three resistors and a voltage source. R1 = 0.18 ohm, R2= 1.15 ohms, R3 = 2 ohms, I=10 amp. Find the voltage drop across each resistor; find the value of voltage in the circuit. Suppose R1 gets open. What does it result in?

4. Two resistors are connected in series. Ri = 7,000, R2= 2,200, I = 110 amp. Find the voltage drop across each resistor. Suppose no current passes through the circuit, what does it result from?

Answer 1

1. The ohmmeter is used to measure the value of resistance while it is connected in paralltl to the resistor.

2. The ammeter is connected in series while the current is being measured.

3. While the value of current in the circuit is measured, the ammeter should be connected in series.

1. Suppose the ammeter scale reads 1.9 amp, the voltmeter scale reads 2.4 V; how much is the value of resistance in the measured circuit?

R = U / I = 2.4 / 1.9 = 1.26 Ohm

2. Suppose the ohmmeter scale reads 75 ohms, the voltmeter scale reads 220 V; how much is the value of current in the measured circuit?

I = U / R = 220 / 75 = 2.9 A

3. Suppose that you have a series circuit consisting of three resistors and a voltage source. R1 = 0.18 ohm, R2= 1.15 ohms, R3 = 2 ohms, I=10 amp. Find the voltage drop across each resistor; find the value of voltage in the circuit.

U1 = R1 * I = 0.18 * 10 = 1.8 V  

U2 = R2 * I = 1.15 * 10 = 11.5 V

U3 = R3 * I = 2 * 10 = 20 V

Suppose R1 gets open. What does it result in? I = 0

4. Two resistors are connected in series. R1 = 7,000, R2= 2,200, I = 110 amp. Find the voltage drop across each resistor.

U1 = R1 * I = 7,000 * 110 = 770,000 V  

U2 = R2 * I = 2,200 * 110 = 242,000 V

Suppose no current passes through the circuit, what does it result from?

It results from the broken circuit.