4. The use of the Internet in the application of psychological treatments
4.3. Internet-based interventions focused on positive affect for depression
1. A 60 W bulb in series with a room heater is connected across the mains. If the 60 W bulb is replaced by 100 W bulb
A. the heater output will increase.
B. the heater output will decrease.
C. the heater output will be same.
D. the heater output will slightly decrease.
The wattage rating of any electrical component (bulb) is inversely proportional to its resistance. Hence 100 W bulb has smaller resistance than 60 W bulb. So if 60 W bulb is replaced by 100 W bulb in the above case then, the overall resistance of the series combination of heater and bulb is reduced hence current increases accordingly. Therefore the output of the heater is increased as the current through it increases.
2. Filaments of electric bulbs are generally made of . nichrome.
A. tungsten.
B. copper.
C. carbon.
Tungsten has the highest melting point of all the non-alloyed metals and the second highest of all the elements after carbon. When current flows through high resistive tungsten filament, it will not melt but glow. That is why filaments of electric bulbs are generally made of tungsten.
3. All the resistances in the circuit given are of R Ω each. The switch is initially open. What happens to the
lamp's intensity when the switch is closed?
. Increases.
A. Remains the same.
B. Decreases.
C. Answer depends on the value of R.
If the all resistances are same (R Ω) then there will be no current in the central Resistance as there is no potential difference [Like Wheatstone Bridge].
4. The ratio of resistances of a 100W, 220V lamp to that of a 100W, 110V lamp will be at the respective
5. Two incandescent light bulbs of 40W and 60W rating are connected in series across a mains then . the 40 W bulb glows brighter.
A. the 60 W bulb glows brighter.
B. the both bulbs glow same brighter.
C. none of these.
Resistance of 40 W lamp is much higher, then the Voltage drop / power consumption will be higher than
the 60 W lamp. So the 40 watt lamp will glow brighter.
R40 > R60
IxR40 > IxR60
I2xR40 > I2R60.
6. The incandescent bulbs rated respectively as P1 and P2 for operation at a specified main voltage are connected in series across the mains as shown in the figure. Then the total power supplied by the mains to
the two bulbs
. P1.P2 ⁄ (P1 + P2).
A. √(P12 + P22).
B. P1 + P2. C. √(P1XP2).
7. Which is a Cold Cathode lamp . Neon lamp.
A. Fluorescent lamp.
B. Mercury vapour lamp.
C. Sodium vapour lamp.
Neon lamp belongs to cold cathode category lamp.
8. How many 200 W ⁄ 220 V incandescent lamps connected in series would consume the same total power as a single 100 W ⁄ 220 V incandescent lamps?
. not possible.
A. 2.
B. 3.
C. 4.
Single incandescent lamp consumes 100W then 2 lamps are required to consume 200W.
9. There are 3 lamps of wattage 40W,60W,80W respectively . Which lamp has the more resistance . All of their resistance are same.
A. 80 W.
B. 60 W.
C. 40 W.
lamp with less wattage has more resistance.
10. Melting point of tungsten filament indegree centigrade is . 3400.
A. 340.
B. 34.
C. 2000.
Melting point and working temperature of tungsten filament are respectively 3400 and 2000 degree centigrade .
11. The cold resistance of a 100W, 200volt imcandescent bulb is ___ohms.
. 60.
A. 320.
B. 480.
C. 400.
R = V2 / W = 200 X 200 / 100 = 400 ohm i.e option D.
12. A metal filament lamp X rated 40 watts, 100 V is connected in series with another lamp Y of the same type nut rated 100 W, 200 V A voltage of 200 V is applied across the combination then
. lamp X gives more light.
A. lamp Y gives more light.
B. Both will be equally bright.
C. none of the lamp will glow.
Because same current passes through the lamps, power developed will be more for 100 W bulb because it has more resistance, so bulb of 100W will glow more bright.
.
13. Name of the fluorescent materials for fluorescence of green colour . zinc silicate + manganese.
A. zinc sulphide+ manganese.
B. zinc sulphide + silver.
C. calcium silicate + manganese.
zinc silicate as base substance with manganese as activator gives green colour .
14. A 100 W light bulb burns on an average of 10 hours a day for one week. The weekly consumption of energy will be
. 0.7 units.
A. 7 units.
B. 70 units.
C. 700 units.
Power: 100 W
Time: 10 x 7 hrs. = 70 hrs.
Energy consumption = 100 x 70 W-hrs.
= 7000 W-hrs.
= 7 KW-hrs.
= 7 Units[ 1 KW-hr = 1 Unit].
15. Tow bulbs marked 200 watts - 250 V, and 100 watts - 250 V are joined in series to 250 V supply. The power consumed by the circuit is
. 33 watt.
A. 200 watt.
B. 300 watt.
C. 67 watt.
The resistance of first and second bulb are (250)2/200 and (250)2/100 Ω respectively. The total resistance when the bulbs are connected in series will be (250)2/200 + (250)2/100 Ω. The total power consumption when they joined in series to 250 V supply. The power consumed in the circuit will be (250)2/{(250)2(1/200 + 1/100)} = 20000/300 = 67 watt.
16. Which of the following is not the unit of electrical power?
. Volt/ampere.
A. Volt ampere.
B. Watt.
C. Joule/second.
Unit of electrical power is watt and watt means joule/second. Again electrical power = voltage × current, hence volt ampere may be another expression for unit of power. But impedance = voltage/current, hence volt/ampere may be expression for unit of impedance not power.
17. ) One kilowatt hour is same as . 36 × 105 watt.
A. 36 × 105 ergs.
B. 36 × 105 joules.
C. 36 × 105 BTU.
Kilowatt hour is the unit of energy and 1 kilowatt hour = 1000 X 1 watt X 3600 second = 36 X 105 watt second = 36 X 105 joule.
18. Two heaters, rated at 1000 W, 250 V each are connected in series across a 250 V, 50 Hz ac mains. The total power drown from the supply will be
. 500 W.
A. 1,000 W.
B. 1,500 W.
C. 2,000 W.
P= 1000 W, V= 250 V
Then, I = 4 A & Resistance of each heater is : 250/4 次 = 62.5 次
In Series connection equivalent resistance will be double :
Req = 62.5 + 62.5 次
19. In a network made up of linear resistors and ideal voltage source values of resistors are doubled. Then the voltage across each resistor is
. doubled.
A. halved.
B. decreased four times.
C. not changed.