O level Physics Current of Electricity

A defibrillator supplies an electric shock of energy 300 J at an average voltage of 2000 V for 10 ms.

What is the average current it supplies?

• 0.015 A

• 0.67 A

• 6.7 A

• 15 A

Two resistence wires made of the same material and of the same length are connected in parallel to the same voltage supply. Wire P has a diameter of 2mm. Wire Q has a diameter of 1mm.

What is the ratio of current in P to current in Q?

• 0.25

• 0.50

• 2.0

• 4.0

When a filament lamp is switched on, there is a current in the lamp. As the temperature of the filament rises, its resistance changes.

Which pair of graphs shows how the resistance R of the filament and the current I vary with time after the lamp is switched on?

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A bird can stand on an overhead high voltage transmission line without getting electrocuted.

Which statement explains the situation?

• Both feet of the bird are at the same voltage

• The bird's body has very high resistance

• The bird's feet are very good insulators

• The air trapped between the bird's feathers act as insulators

40J of energy are delivered by the battery to the resistor. 5 C of charge flow through the resistor in 1.25 s.

Which statement is correct?

• The current flowing through the battery is 6.25 A.

• The electromotive force is 8 V

• The power dissipated by the resistor is 50 W

• The resistance of the resistor is 32 Ω

Identify which switch(es) is/are closed such that all three bulbs are lit.

• Switch P closed

• Switch Q closed

• Switch R closed

Which of the following graph shows the correct I-V relationship for a filament lamp?

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An electron carries 1.6 x 10⁻¹⁹ C. What is the potential difference across a 5 Ω resistor if there are 1 x 10¹⁰ electrons flowing through it in 4 µs?

• 0.002 V

• 2.00 V

• 3.2 x 10⁻¹⁴ V

• 1.28 x 10⁻¹⁵ V

A charge of 7.5 C flows through a resistor in 5.0 s. A student has ammeters with different ranges that he can use to measure the current in the resistor.

Which ammeter range is the most appropriate?

• 0-1 A

• 0-2 A

• 0-5 A

• 0-10 A

The disgram shows the I/V characteristic graphs for two electrical components P and Q

Which of the following statements best describes the two electrical components?

• P is the light-emitting diode and its resistance decreases as potential difference increases

• P is a thermistor and its resistance increases as potential difference increases

• Q is a light-emitting diode and its resistance decreases as potential difference increases

• Q is a thermistor and its resistance increases as potential difference increases.