TEST PAPER - 3
SECTION - I (40 Marks)
Compulsory: Attempt all questions
1)
3)
4) The diagram shows a lens as a combination of a glass block and two prisms .. Answer the following question:
a) Name the lens formed .
b) What are the OX and point F called ?
c) Complete the ray diagram and give the formation image.
d) State the characteristics of the image.
5) An electric iron is marked 200V; 550 W.
a) Calculate the current flowing through it when working.
b) Resistance of filament.
c) Energy consumed in 3 hours of continuous working.
d) Expenditure of energy rated at Rs 2 per unit.
6) What is a transformer.
7) What is the value of
a) a.c voltage supply for household electricity ?
b) frequency of a.c household supply voltage ?
Section - II (40 Marks)
1)
2)
8) Distinguish between a real and virtual image.
9) Two straight wires A and B, carrying strong equal currents in opposite directions , pass through a cardboard as shown in the figure.
What will be the effect on the magnetic field at X, if the current in B is reversed ?
Explain why the lines of force at a distance may differ in shape from those in the immediate vicinity of the conductors.
CURRENT ELECTRICITY
1) A conductor of resistance 4 Ω can pass a current up 2.5 A through it. Calculate the potential difference required across the conductor. 10V
2) Calculate the amount of work done in moving a charge of 5 C through a potential difference of 25V. What will be the potential difference if this amount of work is done in moving a charge of 10C ? 12.5V
3) A metallic wire of length 1m is stretched to double its length in such a way that there is no change in density of the wire . Calculate the ratio of the final resistance. 1:4
4) A wire of length 15m and uniform cross section of 6x 10⁻⁷m² has a resistance of 5Ω. Calculate the resistivity of the material of the wire. 2 x 10⁻⁷Ωm
5) When a potential difference of 4V is applied across the ends of a wire of 10m length, a current of 2A flows through it. Calculate
a) the resistance per unit length of the wire. 0.2Ω m⁻¹
b) the resistance of 4m length of this wire. 0.8Ω
6) A battery supplies a current of 0.8 A through a 2Ω resistor and a current of 0.4A through a 5Ω resistor. Calculate the internal resistance of the battery. 1Ω
7) What will be the equivalent resistance of three resistors of 4Ω, 8Ω and 16 Ω if these are connected in
a) series. 28Ω
b) parallel. 2.28Ω
8) A lamp of resistance 800 Ω, a fire alarm of resistance 30 Ω and a vacuum cleaner of resistance 200Ω are connected in parallel to the mains supply of 240 V. Calculate the current through each appliance and the total current supplied by the mains. 9.5A
9) The effective resistance of two resistors is 25Ω. If the resistance of one of the resistors is 10 Ω, what is the resistance of the other resistors ? 15Ω
10) The effecttive resistance of three resistors connected to a battery is 5 Ω. If R₁ = 10Ω, R₂ = 15Ω, what will be the value of R₃ ? Draw a circuit diagram with the flow of current across each resistor. 30Ω
11) A parallel pair of resistors of values 4Ω and 12 Ω are together connected in series with another resistors of value 3 Ω and battery of emf 24 V. Draw a circuit diagram and calculate the current across each resistor . 3A, 1A
12) The figure below shows
V-I graphs of two metallic conductors for series and parallel combination. Which graph represents parallel combination ?
13) The lengths of three conducting wires of same materials are in the ratio 1:2:3. The area of cross section of each wire is same, if these wires are joined in parallel across a battery, what will be the ratio of the currents in them ? 6:3:2
14) In the given circuit diagram,
the emf of the cell is 5 V and its an internal resistance is 2.5 Ω. Calculate the current flowing in the circuit. 0.67A
15) Find the current flowing through the given circuit connected to a cell of supply 5V. 
3.75A
16) From the circuit flow diagram given below,
Calculate the current flowing through the circuit. 0.67A
17) Three resistors of 8Ω, 4 Ω and 2 Ω are connected together in such a way that the total resistance is greater than 8Ω but less than 10 Ω. Suggest a suitable arrangement of how these resistors can be possibly combined and calculate the total resistance. 9.33Ω
18) In the given diagram,
A₁, A₂ and A₃ are three ammeters of negligible resistance. The reading of ammeter A₃ is 1A. Calculate
a) the readings of ammeter A₁ and A₂. 3A
b) the total resistance of the circuit. 2Ω
19) The diagram below
shows three resistors of 5Ω, 8Ω and 10Ω connected to a battery of emf 10V. Calculate
a) the potential difference across the parallel resistors 8Ω and 10Ω. 4.7V
b) the current through 8Ω resistors. 0.59A
20) A cell of emf 2.5 V and internal resistance 1.5 Ω is connected to resistors of 5 Ω and 15Ω in series. Draw a circuit diagram and calculate
a) the current in the circuit. 0.116A
b) the potential difference across each resistor. 1.74V
c) the total potential difference across the cell. 2.32V
21) An electric motor draws a current of 5 A from a 220V line. Determine the power of the motor and the energy consumed in 2 hour. 7.92 x 10⁶J
22) A heater has a power of 1.1 kW at 220V.
a) Find the resistance of the heater. 44Ω
b) Calculate the energy in kWh consumed in a week if the heater is used daily for 4h. 30.8 kWh
23) An electric heater draws 5A of current for 10 minute when connected to 230V power supply. Find the heat energy developed. 690 kJ
24) Find the current flowing through an electric bulb rated as 100W, 220V when connected to a 110 V supply. What will be the power consumed now? 25W
25) Three bulbs, A, B and C, are connected in parallel across 110V source . The rating of bulb is 5oW, 110V, bulb B is 20W,110 V and bulb C is 100 W, 110V
a) Calculate the current flowing in each bulb. 0.45A, 0.18A, 0.9A
b) Which bulb will glow the brightest ? C
26) Two resistors with resistance R₁ = 5Ω and R₂=7Ω are connected in series across a battery of emf of 16V. Draw a circuit diagram and find
a) the electrical energy consumed by each resistor in 30 second.265.33J, 371.47 J
b) total power developed in the circuit. 21.28 W
27) In the previous example, if the resistors are connected in parallel instead of series, what would be the electrical energy consumed by each resistor. Draw a circuit diagram for the same. 1536 J, 1097.14 J
28) two bulbs are rated as 40W, 220 V and 40W, 110 V, respectively. Compare the resistance of two bulbs. 4:1
29) A geyser is rated 1.5kW, 250V. It is connected to 250V mains. Calculate
a) the current drawn by the geyser. 6A
b) electrical energy consumed in 10h in joules. 54 x 10⁶ J
c) cost of energy consumed at Rs3.50 per kWh. Rs52.50
30) Four tube lights of 40 W each, two fans of 100W each and three bulbs of 60W each operate on an average of 8h per day. If the cost of energy is Rs2.50 per kWh, calculate the monthly bill. Rs324
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