Self Test

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1.

A cell of EMF 2.0 V and internal resistance 0.5 ohms is connected in series with an ammeter and a torch bulb.  The ammeter reads 0.25 A

 

 

(a)

Sketch the circuit diagram in the space below.

3

 

 

 

 

(b)

Show that the potential difference across the bulb is about 1.9 V

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(c)

Calculate the power delivered to the bulb.

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(d)

Calculate the power delivered by the cell.

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(e)

Explain why the power delivered to the bulb is less than the power delivered by the cell.  Refer to your answers above.

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13

2.

A circuit is shown below:

 

 

 

 

 

 

 

 

 

 

 

 


 

(a)

What is meant by Thévenin’s Theorem?

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(b)

Calculate the Thévenin voltage across the 14 ohm resistor

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(c)

Work out the Thévenin resistance in the circuit

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(d)

Work out the current in the 14 ohm resistor.

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(e)

Calculate the power in the 14 ohm resistor

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(f)

Work out the efficiency of the power transfer

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16

Answers

Note that the answers were scanned in, so Question 1 is shown as Question 2, and Question 2 is Question 3.

Very hippy lazy of me.