Current and potential differenceIB MYP Physics: Subtopic test

1. 1
   A camping torch has a small lamp that is powered by a 6.0 V battery. A family on a night walk in the Hajar Mountains switches the torch on and leaves it running for a short time.

   (a)

   The lamp carries a steady current of 0.50 A for 2.0 minutes. What charge flows through the lamp in this time?

   [1 mark]

   • A0.0042 C
   • B240 C
   • C60 C
   • D120 C

   (b)

   Which statement correctly defines electric current?

   [1 mark]

   • AThe rate of flow of charge
   • BThe energy transferred per unit charge
   • CThe opposition to the flow of charge
   • DThe amount of energy stored in the battery

   (c)

   Calculate the energy transferred to the lamp when 60 C of charge passes through it from the 6.0 V battery.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A student builds a simple circuit from a cell, a switch and a lamp, joined together with copper wires. She wants to find out how charge moves in the wires and to measure the current through the lamp and the potential difference across it.

   (a)

   Which particles carry the current in the copper wires?

   [1 mark]

   • AProtons
   • BPositive ions
   • CNeutrons
   • DFree electrons

   (b)

   How should the ammeter and the voltmeter be connected?

   [1 mark]

   • ABoth in series with the lamp
   • BThe ammeter in series with the lamp and the voltmeter in parallel across the lamp
   • CThe ammeter in parallel across the lamp and the voltmeter in series with it
   • DBoth in parallel across the lamp

   (c)

   State the direction of conventional current in the circuit and explain why this is opposite to the direction in which the electrons move.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A student investigates how the current through a small filament lamp depends on the potential difference across it. She connects the lamp to a variable power supply, with an ammeter and a voltmeter, and measures the current for four different values of potential difference.

   (a)

   State a testable hypothesis for this investigation, give a scientific reason for it, and identify the dependent variable.

   [3 marks]

   (b)

   Her results were: 1.5 V gave 0.10 A, 3.0 V gave 0.19 A, 4.5 V gave 0.27 A and 6.0 V gave 0.33 A. State the trend in the results. Then calculate the charge that passes through the lamp in 30 s when the p.d. is 3.0 V, and the energy transferred to the lamp in that time.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A charity plans to give 500 rural families in Kenya a torch with a rechargeable 3.7 V battery, charged by a small solar panel, to replace torches that use disposable cells. Many of the families have no mains electricity, and children currently study in the evening by the light of kerosene lamps.

   (a)

   In one evening the lamp in the new torch carries a steady current of 0.40 A for 2.5 hours. Calculate the charge that flows through the lamp and the energy transferred to it. Explain what the 3.7 V means.

   [6 marks]

   (b)

   Evaluate whether the charity should give out the rechargeable solar-charged torches rather than torches with disposable cells.

   [6 marks]

   Total for question 4: 12 marks

End of questions