1) Current is the flow of electrons through a conductor and is measured in Amperes. It flows from the positive terminal to the negative terminal in a circuit with a potential difference. 2) Alternating current changes direction periodically while direct current flows in only one direction. AC is preferred for transmission due to lower energy losses while DC is used for applications like batteries. 3) A resistor limits current flow in a circuit. It offers resistance and converts voltage to heat energy. Resistors are used to control current and divide voltages in a circuit. Their values can be determined using color codes.

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2. Mand Labs presents
Current & Resistance

3. Current
• Current- Amount of charge (number of electrons ✕ charge on 1
electron) crossing through a particular section in one second
• Why Electrons flow- Potential difference & Closed Path
• Direction of Current is taken as opposite to movement of electrons

4. Current from battery
• 9V Potential Difference
• An external path/circuit
between +ve and -ve
• Current flows from +ve
terminal to -ve terminal
• Direct Current (DC)

5. • Unit of Current is Ampere
• Ampere is expressed as A
• Examples: 2.5 A, 3 A, 100 A, 423.55 A
• Symbol is I
• Current Rating- Max. current that you can safely pass
through a device before you can fuse it
Current

6. Alternating Current
• Does not mean just mean
fluctuating
• Direction of current keeps changing
• Both +ve and −ve voltage (or
current) cycles in the current
• Preferred for transmission and high
voltages
• Minimal Energy Loss in transmission
• Examples: Air Conditioner, Electric
Iron, Water Cooler run on AC

7. Direct Current
• Unidirectional current
• Either complete +ve or -ve
votlage (or current) cycles
• Energy Loss is substantial
• Preferred for low voltage
applications
• Examples: Car, Mobile Phone
run on DC battery

8. If floor is too smooth, you will not be able
to walk. You need some roughness.
In electricity, we can create friction to the
flow of current using a resistor.
Resistor

9. • Limits the flow of current
• Conductor: Offers less resistance to the flow
• Insulator: Offers infinite resistance to the flow
• Eats away voltage and converts it into heat
energy (joule heat)
• Voltage drop- The voltage it eats away
• Resistor offers Resistance
Resistor

10. • Main Uses:
‣ Control the amount of current in a circuit
‣ Divide voltage in a circuit
• Unit is Ohm and expressed as Ω
• Examples: 10R Ω, 10 kΩ, 10 MΩ, 4k7 Ω
Resistor
Schematic Symbol

11. • Meanings:
• 10R = 10 Ω
• 10k = 10 Kilo = 10 × 1000 = 10,000 Ω
• 10M = 10 Mega = 1000,000 = 10,000,000 Ω
• 4k7 = 4.7k = 4.7 × 1000 = 4700 Ω
• Remember: 1k (kilo) = 1000 = 103 and 1M (Mega) = 106
Units

12. 1) Ist Band - Orange
2) 2nd Band - Orange
3) 3rd Band - Brown
4) 4th Band - Gold
Color Coding
Reading Resistance

13. B
B
R
O
Y
G
B
V
G
W
Readfirstalphabetofcolor
BB Roy Great BritainVery Good Wife
Color Band Table

14. Formula: 1st digit 2nd digit × 103rd digit ± y%
No. Color Digit
1 Orange 3
2 Orange 3
3 Brown 1
4 Gold 5%
33 × 101 ± 5% = 330 Ω ± 5%
➡ First Color Band - 1st digit
➡ Second Color Band - 2nd digit
➡Third Color Band- 3rd digit
➡Fourth Color Band - y %
➡ y is known as Tolerance
➡Tolerance is the % by which the
resistance value will vary
Color Code Formula

15. Another example
No. Color Digit
1 Brown 1
2 Black 0
3 Orange 3
4 Gold 5%
10 × 103 ± 5% = 10,000 Ω
= 10 kΩ

16. Measure R using a Multimeter
• Rotate the dial to Ω region
• Set the appropriate range
• Range Available: 200 to 2000k
(2000k = 2000,000)
• If the dial is on 20k or 200k or
2000k, multiply the meter
reading by 1000 to get the
actual value
• If you get 1 on the left hand
side of the display, increase the
range

17. Steps to measure R
• Set the meter dial to
2000 in Ω region
• Connect the probes
across the two legs of
the resistor
• A resistor does not have
any +ve and -ve
Multimeter Reading = 330 Ω
Color Code - Orange Orange Brown Gold

18. Example: Color Code
• Pick up a resistor with
color code: Brown Black
Orange Gold
• Meter shows reading 1 on
the 2000 Ω range
• Increase the range to 20k
(in next slide)

19. Example: Measure R
• Note down the reading
• Since the meter dial is on
20k, multiply the reading
with 1k = 1000 to get
the actual value
Reading = 10.07, Value = 10.07 × 1000 = 10 kΩ

20. Ohm’s Law
• Defines relation betweenV (voltage),
R (resistance) and I (current)
• R =V/I = constant (ratio is constant)
• Voltage = Current × Resistance
• V = R I
• Example: If V = 9V, R = 1 kΩ
• I =V/R = 9/1000 = 0.009 A = 9 mA
(1milli = 1m = 1/1000)

21. Ohm’s Law Triangle

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