Three voltmeters V, V₁ and V₂ are connected as in Figure 37.9. a If V reads 18V and V, reads 12V, what does V₂ read?

b If the ammeter A reads 0.5A, how much electrical energy is changed to heat and light in lamp L₁ in one minute? c Copy Figure 37.9 and mark with a + the positive terminals of the ammeter and voltmeters for correct

connection.

a. V₂ = 6 V

b. 360 joules

c. The positive terminals of both the voltmeter and ammeter are connected to the positive terminal of the power source

Please see the attached drawing created with MS Visio

Explanation:

a. The voltmeter readings are;

V₁ = 12 V, V = 18 V

Given that the voltage reading, 'V', is the voltage reading across two loads with voltages, V₁ and V₂ connected in series, we have;

V = V₁ + V₂

V₂ = V - V₁

V₂ = 18 V - 12 V = 6 V

b. The reading of the ammeter, A, I = 0.5 A

The heat energy, Q  = I·V·t

Where;

t = The time = 1 minute (60 seconds)

Therefore, for the lamp L₁, where V = 12 V, we have;

Q₁ = 0.5 A × 12 V × 60 s = 360 Joules

The amount of electrical energy changed into heat and light in lamp L₁, Q₁ = 360 joules

c. The positive terminals of the voltmeter and ammeter are connected to the positive terminal of the power source

Please see attached drawing created with MS Visio

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