PHYSICS ASSIGNMENT (CURRENT)
E = 6V,r = 2Ω
A
B
7Ω
4Ω
Figure 1.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
4µF A
6µF
6Ω
4Ω
B
12 V r = 1Ω
Figure 2.
A bulb can be operated at a maximum 150 volt. Its resistance is 200 ohm. How will you use it at 210-volt mains.
On connecting two wires at series the resultant is 16 Ω and when in || the resultant is 3 Ω. Find them?
Show that the unit of farad-ohm is time.
Potential difference of V is applied across the ends of a copper wire of diameter d and length l . what will be the
effect on the drift velocity of the electrons if (i) V is doubled. (ii) l is doubled (iii) d is doubled.
60 V is connected is across series combination of 300 Ω and 400 Ω. Voltmeter is connected across 400 Ω and
reading is 30 V. Find the reading when it is connected across 300 Ω resistance.
2 cells of emf 11 V and 9 V and internal resistances 1 Ω and 2 Ω are joined in || to send the current in same direction
and connected across 24 Ω R. Find the i from each cell and terminal potential difference.
Repeat the Q No. 6 if cells are connected to oppose current.
What will be the effect on position of zero deflection in potentiometer if (i) emf of experimenting cell be decreased
(ii) current through potentiometer be decreased (iii) length of wire be doubled? Halved?
ABCD is a square frame. Arm AB = 90 Ω., BC = 110 Ω, CD = 60 Ω, DA = 40 Ω.battery of 4 V is connected across
AC. Find the potential difference across BD.
Find the potential difference between A and B in Fig. 1 and Fig. 2.
PHYSICS ASSIGNMENT (CURRENT)
E = 6V,r = 1Ω
A
B
7Ω
4Ω
Figure 1.
4µF A
6µF
6Ω
3Ω
B
12 V r = 1Ω
Figure 2
1. A bulb can be operated at a maximum 150 volt. Its resistance is 200 ohm. How will you use it at 210 Volt mains?
[80Ω]
2. On connecting two wires at series the resultant is 16 Ω and when in || the resultant is 3 Ω. Find them? [12Ω,4Ω]
3. Show that the unit of farad-ohm is time.
4. Potential difference of V is applied across the ends of a copper wire of diameter d and length l. what will be the
effect on the drift velocity of the electrons if (i) V is doubled. (ii) l is doubled (iii) d is doubled.
5. 60 V is connected is across series combination of 300 Ω and 400Ω. Voltmeter is connected across 400 Ω and
reading is 30 V. Find the reading when it is connected across 300 Ω resistances. [22.5 V]
6. 2 cells of emf 16 V and 18 V and internal resistances 1 Ω and 2 Ω are joined in || to send the current in same
direction and connected across 6 Ω. Find the i from each cell and terminal potential difference. [1.5 A, 1 A 15 V]
7. Repeat the Q No. 6 if cells are connected to oppose current. [11.8 A, 11.1 A, 4.2 V]
8. What will be the effect on position of zero deflection in potentiometer if (i) emf of experimenting cell be decreased
(ii)current through potentiometer be decreased (iii) length of wire be doubled? Halved?
9. ABCD is a square frame. Arm AB = 90 Ω., BC = 110 Ω, CD = 60 Ω, DA = 40 Ω.battery of 4 V is connected across
AC. Find the potential difference across BD. [1.8 − 2.4 V]
10. Find the potential difference between A and B in Fig. 1 and Fig. 2. [5.5 V] [7.2 V − 6.48 = 0.72 V]
DHAWAN COACHING CENTER 3259940; 4232206; 09350245008
CURRENT ELECTRICITY
1. Current in series circuit is 5A. When an additional resistance of 2 Ω is added the current drops
to 4 A. Find original resistance ?
2. Show that dimensions of Farad-ohm & time are same.
3. Potential of 'V' is applied across conductor of length ‘l’ and radius 'r'. How do E, & vd Change
when (i) V is doubled (ii) l is halved (iii) 'd' is doubled?
4. When resistance of 75 Ω is connected to battery 0.5A flows. If resistance is increased to 115Ω.
Current is 1/3 A Find 'E' & 'r'?
5. Resistance of 250 Ω, voltmeter and 2.0 V cell is in series. Find the resistance of voltmeter if
reading of voltmeter is 0.8 V?
6. An arc lamp operates at 80 V and takes 10 A. Find necessary resistance to use at 240 V.
7. Electric fan at 110 V takes 3.5 A. if it is connected across 125 V. Find necessary resistance?
8. Two cells of emf 3V & 1.5V, and internal resistance 1Ω & 0.5Ω are connected in parallel across
2Ω. Find the current from each cell?
9. Length of 3 wires in ratio of 2:3:4 and radii in ratio of 3:4:5. They are connected in parallel and
included in circuit having 5 A. Find the current each wire?
10. 400 Ω and 300 Ω are connected in series across 60V supply. Voltmeter connected across 300 Ω
reads 30 V. Find the reading when it is connected across 400 Ω?
11. Find current each resistance through R1, R2 & R3 in all the cases, even when K is open/close
(R1= 18 Ώ, R2 = 12 Ώ, R3 = 24 Ώ, R4 = 12 Ώ)
12. In Figure if B is grounded find potential at all the other points.
13. Find the reading of Voltmeter and Ammeter in all circuits (R1 = 500 Ώ, R2 = 600 Ώ}
14. ABCD is a square such that each side has resistance of 1Ω. Find point E on CD such that if 1Ω
is connected across A & E, and battery across AC points B & E are equipotential.
15. Find current through each resistance in both networks
16. R1 = 10 Ώ, R2 = 20 Ώ and R3 = 30 Ώ. Φ1 = 10 V, Φ 2 = 6 V, Φ 3 = 5 V .Find the current through
each resistor
DHAWAN COACHING CENTER 3259940; 4232206; 09350245008
2012
1. There is a current of 1.0 A in a copper wire of length 0.10 m and area of cross section 1.0 × 10−6 m2. (i)
What is current density in the wire? (ii) If there be 1 free electron per atom in copper, then determine the
drift velocity of electrons. (Given: density of copper = 89 × 103 kg/m3, atomic weight = 63.5, N = 6.02 ×
1026 per kmol, e = 1.6 × 10 −19 C). [Ana. 7.4 × 10 −5 m/s]
2. Two wires A and B of equal masses and of the same metal are taken. The diameter of the wire A is half the
diameter of the wire B. If the resistance of the wire A be 24 ohm, calculate the resistance of the wire B.
[Ans. 1.5 ohm]
3. A 200 V bulb takes a current of 0.2 A. The length of its filament is 22 cm and the specific resistance of the
material of the filament is 7 × 10 −5 Ωcm. Find the radius of the filament (π = 22/7). [Ans. 7 × 10−4 cm]
4. A voltmeter of resistance 998 Ω is connected across a cell of emf 2 V and internal resistance 2 Ω. Find the
p.d. across the voltmeter, that across the terminals of the cell and percentage error in the reading of the
voltmeter. [Ans. 1.996 V, 0.2%]
5. n the given circuit a p.d. of 220 V is applied across a 12000 Ω rheostat AB. A 6000 Ω voltmeter V is
connected between A and a point C, where AC = (1/4) AB. What does the voltmeter read ? [Ans. 40 V]
6. A 15 V dc source is connected across the series combination of a 100 Ω and also 150 Ω resistor, as shown
in Fig. A voltmeter reads 7.5 V when connected across the 150 Ω resistor. What would it read when
connected across the 100 Ω resistor? [Ans. 5.0V]
7. A potentiometer wire of length 200 cm has a resistance of 20 Ω. It is connected in series with a resistance
of 10 Ω and an accumulator of emf 6 V having negligible internal resistance. A source of 2.4 V is balanced
against a length L of the potentiometer wire. Find the value of L. [Ans. 120 cm]
8. The adjoining circuit diagram represents balanced wheat stone’s bridge, calculate R. [Ans. 3.75 Ω]
9. Calculate the voltage drop across the 18 Ω resistor in the given circuit. The emf of cell is 60 V.[Ans. 45V]
10. A 10 m long potentiometer wire has a potential gradient of 0.0025 V/cm along its length. Calculate the
length of the wire at which null point is obtained for a 1.025 V standard cell. Also find the emf of another
cell for which the null- point is obtained at 860 cm length. What maximum pd can be measured by this
potentiometer? [Ans. 410 cm, 2.15 V, 2.5 V]
11. A series battery of six lead accumulators, each of emf 2.0 V and internal resistance 0.50 Ω is charged by a
100 V dc supply. What series resistance should be included in charging circuit to limit the current to 8.0 A
? Find (a) the power supplied by the dc source, (b) the power dissipated as heat and (c) the energy stored in
the battery in 15 minutes. [Ans. 8.0 Ω, (a) 800 W, (b) 704 W, (c) 86400J]
12. There are two electric bulbs rated 60W−110V and 100W−110 V. They are connected in series with a 220
V dc supply. Will any bulb fuse? What if they are connected in parallel with the same supply?[Ans. 60W
bulb will fuse, while the 100W bulb will light up dim, both bulbs will fuse]
13. A heating coil of 2000 W is immersed in an electric kettle. How much time will it take in raising the
temperature of 1 litre of water from 4°C to 1000 C? Only 80% part of the thermal energy produced is used
in raising the temperature of water. [Ans. 251 seconds]
14. A 50W bulb is connected in a 200V line. Find its resistance and current flowing through it. If only 100%
of the power is converted into light energy, at what rate heat would be produced in the filament of the
bulb? [Ans. 800 Ω, 0.25 A, 10.8 cal/s]
15. A heater coil is rated 100 W. 200 V. It is cut into two identical parts. Both parts are connected together in
parallel, to the same source of 200 V. Calculate the energy liberated per second in the new combination.
[Ans. 400 W]
DHAWAN COACHING CENTER 3259940; 4232206; 09350245008