Resistance is a measure of the opposition to current flow in electrical circuit. resistance is measured in OHM.
Register is a passive component with the primary function to limite the flow of current.
- basically resistor are used to limit the current and reduce the voltage flow through the circuit (unit of resistance is ohm)
Equation of resistance:
The resistance( R )of a given material is proportional to its length( l )and inversely proportional to its area of cross section. Therefore, the resistance of a material is given by the symbolic re presentation of resistor .• There are two types of resistors : fixed resistors and variable resistors. If the electrical resistance value is constant, it is a fixed resistor. If the electrical resistance value is adjustable, it is a variable resistor. Rheostat and potentiometers are examples.
FIXED RESISTOR:
A fixed resistor is a part of an electric circuit. It is used to reduce the flow of electricity in an electric circuit.
Variable Resistors
These are three-terminal devices. Two terminals arefixed while the third one is connected to a movable cap which slides along the element, changing the resistance between end terminal and tap terminal. They are also called potentiometers, trimmers and rheostats. Potentiometers are designed for frequent and continuous movement of the Trimmers are used only for occasional movement of the tap Rheostat is a wirewound variable resistor of higher wattage with three terminals.jpg)
PROPERTIES OF RESISTOR:1.tempreture cofficient of Resistor: The change in resistor value due to temperature is indicated by temperature coefficient.
2.Voltage Coefficient of Resistor: This is indicated by the voltage coefficient of resistor. It is defined as the percentage change in resistance from the purchase resistance of a resistor when 1 volt DC is applied.
3.Stability: It is the change in resistance value under shelf life or working conditions. Due to good stability
4.Maximum Operating Voltage: its value and power rating together décide the maximum operating voltage.
5.Size:the value of resistor are depend on his size
6.Shelf and Load Life: A good resistor should not change its value under working conditions as well as under idle conditions.
7. Power Handling Capacity : It is the maximum wattage that a resistor can dissipate without the excessive heat. From power rating, the maximum current a resistor can carry safely can be found. Carbon resistors have less power handling capacity.
8.Maximum Operating Temperature: The coating used on the resistors decides the maximum operating temperature of the resistors.
9.Thermal Noise:
10.Tolerance: The tolerance is specified as a percentage of nominal value, i.e., ±5%, ±10% of nominal value. When no tolerance is given, then 20% is assumed.
11.frequency range:
12.Solderability :
13. Current Noise: When current flows through the resistance, low frequency noise is caused by the current.
•SYMBOL OF RESISTOR
1.
 |
Fixed value resistor IEC
|
2.
 |
| Fixed value resistor IEEE |
3. |
| Variable resistor rheostats |
4. |
| Variable resistor potentio metere |
5. |
| Light depend resistor LDR |
•colour code of resistor:
Normally a resistor have four colour code
- 1st colour and 2nd colour code are shown digit
- 3rd colour code shown multiplier
- 4th colour code are shown tolerance
1.which of the following also called variaster
a)PTC b)NTC
C)VDR d) LDR
ans=c
1-PTC = positive tempreturne cofficient ( sensistor)
2- NTC= Negetive tempreture cofficient ( thermistor)
3- VDR = voltage Depended resistor
4- LDR = light depended resistor. (varistor )
2. colour code of a resistor is Red Black, Red Resistor value will be
red-2 ,Black =0 ,Red = Multiplier=10 square =100
red, black first two digit 2,0 =20
20x10² = 20×100 = 2000 ohm (2k ohm also called)
3. Resistor is a device?
Ans= Biloterial Resistor
4. The tallarance of silver is
A) 1% B) 0.5%
C) % 10 D) 5%
Ans= c
5. Which of the following is a linear resistor?
A) Wire wound resistor
B) Thermistor
C) LDR
D) VDR Ans = A
( There are two types of Resistor 1. Linear, 2.non linear
Thermistor,LDR and VDR are comes under non linear and wire wound Resistor are comes under linear Resistor )
6.To what minimum value can the resistance be set in a potentialmeter?
A) Zero
B) 1 ohm
C) 10 ohm
D) 1kilo ohm Ans = A
the minimum value of a Resistor is zero
7. The physical size of the resistor is determined by....
A) Power value
B) Voltage value
C) Current value
D) resistance value
ans= A
8. Which of the following is a fixed value
resistor?
A) Potentiometer
B) Rehostat
C) Trimmer resistor
D) Carbon film resistor. ans= D
potentiolmeter , rheostats and trimmer is under variable resistor
9. Which of the following types of resistors are made in high wattage?
A) Carbon composition resistor
B) Metal film resistor
C) Carbon film resistor
D) Wire wound resistor ans= d
10. Colour code red, green, orange, silver resistors will have a minimum resistance value
A) 25000 ohm
B) 22500 ohm
C) 23500 ohm
D) 21500 ohm. Ans=b
red = 2 , green= 5 ,orange multiplier = 1000 siver tatrace = 10%.
25×1000=25000
10% of 25000 is 2500
Minimum value 25000-2500= 22500
maximum value 25000+2500 =27500
11. Carbon films Resistor are made in resistive capacity.
A) 1Ω-10 MΩ
B) 1 Ω - 100 ΚΩ
C) 1 Ω - 100 ΜΩ
D) 1 Ω - 22 ΜΩ. Ans = A
Carbon film Resistor =1 Ω-10 MΩ
carbon composition=1 Ω - 22 ΜΩ.
wire wound Resistor= 1 Ω - 100 ΚΩ
12. How many ohms can the value of resistance of color code brown, black, black, brown, change?
A) 100 ohm
B) 1 ohm
C) 10 ohm
D) 0.1 ohm ans =d
Brown=1 ,Black = 0 , Black Multiplier =10°
brown tallarance= 1%
then,
10X10° = 100
10/1%= 0.1ohm
13. Trimmer potentiometer is a type of......
A) Fixed resistor
B)Variable resistor
C) Fixed capacitor
D) Variable capacitor. Ans=B
14. Which of the following resistors is better?
A) 1 kΩ, 10% tolerance
B) 1 kΩ, 20% tolerance
C) 1 kΩ, 2% tolerance,
D) 1kΩ 5% tolerance. ans=c
15. The high wattage rotary type rheostat, which is used to change ac main supply voltage, is called?
A) Variac
B) Auto transformer
C) Tap changer
D) Bosteer ans=A
16. M1M1W is inscribed in the letter code method on a resistor. Its value will be ....
A) 1 MΩ, 10% tolerance, 1W
B) 1.1MΩ, 10 % tolerance, 1W
C) 1 MΩ, 20% tolerance, 1W
D) 1.1 MΩ, 20% tolerance, 1W. ans=C
17. Colour code brown, black, black, resistance value
A) 100 ohm
B) 1 ohm
C) 10 ohm
D) 1 kilo ohm. ans=C
brown= 1 ,black = 0
10×1= 10 ohm
18. NTC resistor also known as...
A) Sensitor
B) Thermistor
C) Varistor
D) None above. ans=B
sensiter =PTC. ,thermister = NTC
Varistor = VDC
19. According to which of the following a resistor is not classified?
A) Nominal value, in kΩ, kΩ, MΩ
B) Power rating, in W, KW
C) Voltage rating, in V, KV
D) Types of resistor. Ans=C
20. M11 typed on a resistor, its value will
be...
A) 110 ΚΩ
B) 11 ΜΩ
C) 110 ΜΩ
D) 1100 ΚΩ. ans=A
21. Which of the following is not a PTC ?
A) Copper
B) Aluminium
C) Nichrome
D) Carbon. ans=D
copper , aluminum , Nichrome = PTC
carbon =NTC
22. In the band of resistive colors, if the 3rd band is of silver then the resistance value ...
A) less than 1 ohm
B) less than 10 ohm
C) less than 100 ohm
D) in between 1 ohm to 10 ohm. ans=A
if the of 3rd bond is silver then value of resistance is less then 1
23. A device used to limit current values that can be used equally in both electrical and electronics?
A) Resistor
B) Capacitor
C) Inductor
D) Conductor. ans=A
24. Which metal is used to make wire wound resistors?
A) Nickel chromium alloy (nichrome)
B) Copper nickel manganese alloy (manganin)
C) Tungsten
D) All above. Ans =D
25. The nominal value of resistance has a tolerance of 5%. Its 3rd band is ...
A) Silver
B) Golden
C) Violet
D) Gray. ans=golden
26. how many terminals in a Variable Resistor
A) 1
B) 3
C) 4
D) 6. ans=B
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.jpg "Colour code of resistor")
.jpg "Resistor")
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