This document discusses ammeters, voltmeters, and resistance in series circuits. It defines an ammeter as an instrument used to measure electric current and notes that it is always connected in series. A voltmeter is defined as measuring potential difference and is always connected in parallel. When resistances are connected in series, the current through each is the same but potential difference across each is different. The equivalent resistance of resistors in series is equal to the sum of the individual resistances. Some example calculations are shown for finding equivalent resistance.

1. Electricity
Class – 10
Aditya Mishra
Email: adityakumar2009@gmail.com
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2. Ammeter :
• An instrument used to measure the amount of electric current
flowing through an electric circuit is called ammeter.
• Always connected in series
Symbol :
AMMETER
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3. AMMETER
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4. VOLTMETER
Voltmeter :
• An instrument used to measure the potential difference
between any two point in an electric circuit is called voltmeter
• Always connected in parallel
Symbol :
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5. VOLTMETER
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6. RESISTANCE IN SERIES
R1 R2 R3
• Current through (I) the resistances is same
• Potential difference (V) across each resistor is different
I I
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7. 1 2 3
Total potential difference:
V = V + V + V
V = I R
1 1
V = I R
2 2
V = I R
3 3
V = I R
1 2 3
I R = I R + I R + I R
 
1 2 3
I R = I R + R + R
 
1 2 3
R = R + R + R
eq 1 2 3
R = R + R + R
------- (1)
------- (2)
------- (3)
------- (4)
------- (5)
Substituting equation 2,3,4 and 5 in equation 1
------- (6)
RESISTANCE IN SERIES
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8. eq
R = R + R + R
eq
R = 3R
eq
R = R + R + R + .......
eq
R = n R
---------------- (7)
---------------- (8)
• Equivalent resistance for three resistances each having a value of
R in series combination :
• Equivalent resistance for ‘n’ resistances each having a value of
R in series combination :
RESISTANCE IN SERIES
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9. Q.1 Three resistances each of 3 ohms are connected in series.
Find the equivalent resistances for the combination ?
R = 3 Ω
n = 3 
eq
R = ?
Given :
To Find :
Solution :
For series combination
eq
R = n R
eq
R 3 3
 
R = 9 
Ans :
Problems
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10. Q.1 A 100 resistances when arranged in series combination the
equivalent resistance of the combination is 5000 ohms. What is
the resistance of each resistor ?
n = 100
eq
R = 5000 
R = ?
Given :
To Find :
Solution :
For series combination
eq
R = n R
eq
R
R =
n
5000
R =
100

R = 50 
Problems
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