Current and electricity are core topics in physics, encompassing electric current, circuits, resistance, and the behavior of electrons. Key areas that can be tested include the nature of electric current. Another key area is Ohm’s law, Series and parallel circuits, the heating effect of electric current among others
Questions
- Figure 1 shows four identical bulbs connected to a 15 volt battery whose internal is negligible.
Determine the reading of the voltmeter V. (2 marks).
2. Figure 14 shows a circuit in which a battery. a switch , a bulb, resistor P, a variable resistor Q. a voltmeter V and two ammeters A1 and A2 of negligible resistance are connected.
P has a resistance of 10 Ω. When the switch is closed A1 and A2 reads 0.10 A and the voltmeter reads 1.5 V.
(a) Determine;.
(i) the current passing through P; (3 marks).
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
(ii) the resistance of the bulb (2 marks).
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
(b) The variable resistor Q is now adjusted so that a larger current flows through A2 .
(i) State how this will affect the resistance of the bulb (1 mark)
----------------------------------------------------------------------------------------------------------------------------------------------------
(ii) Explain your answer in (b)(i). (3 marks)
------------------------------------------------------------------------.
------------------------------------------------------------------------.
------------------------------------------------------------------------.
------------------------------------------------------------------------.
------------------------------------------------------------------------.
------------------------------------------------------------------------.
------------------------------------------------------------------------.
(c) A house has one 100W bulb, two 60W bulbs and one 30W bulb. Determine the cost of having all the bulbs switched on for 70 hours,. given that the cost of electricity is 40 cents per kilowatt hour. (3 marks).
- 3. (a) Define current stating its S.I units. (2 mark)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
(b) A battery circulates charges round a circuit for 1.5 minutes. If the current is held at 2.5 Amperes, what quantity of charge passes though the wire? (2 marks)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
4. Figure 2 shows arrangement of three capacities of 10µF, 2µF and 5µF.
Determine the effective capacitance. (3 marks)
5.(a) Figure 8 shows a graph of potential difference V (volts) against a current I(amperes) for a certain device.
From the graph:
(i) State with a reason whether or not the device obeys ohms law. (2 marks)
(ii) determine the resistance of the device at ;
(I) I =1.5 A (2 marks)
(II) I = 3.5 A (2 marks)
(iii) From the results obtained in (ii) state how the resistance of the device varies as the current increases. ( 1 mark)
(iv) State the cause of this variation in resistance. (1 mark)
5(b) Three identical dry cells each of e.m.f 1.6 V are connected in series to a resistor of 11.4 ohms. A current of 0.32A flows in the circuit. Determine:
(i) The total e.m.f of the cells (1 mark)
(ii) The internal resistance of each cell; (3 marks)
6. Figure 6 below shows an electric generator. The points P and Q are connected to a cathode ray oscilloscope (CRO).
Sketch on the axes provided the graph of the voltage output as seen on the CRO, given that when t=0 the coil is at the position shown in the figure. (2 marks).
7. A 60 W bulb is used continuously for 36 hours. Determine the energy consumed. Give your answer in kilowatt hour (kWh). (3 marks)
8. Figure 8 shows the cross-section of a dry cell. Use the information on the figure to answer questions 4 and 5.
Name the parts labelled A and B. (2 marks)
8 (b) State the use of the manganese(IV) oxide in the cell. (1 mark).
9. A 4 ohms resistor is connected in series to a battery of e.m.f 6.0 V and negligible internal . Determine the power dissipated by the resistor (2 marks)
10. State the reason why electrical power is transmitted over long distances at very high voltages .(1 mark)