The document Solutions of Electricity (Page No- 41) - Physics By Lakhmir Singh, Class 10 Class 10 Notes | EduRev is a part of the Class 10 Course Class 10 Physics Solutions By Lakhmir Singh & Manjit Kaur.

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**Lakhmir Singh Physics Class 10 Solutions ****Page No:41**

**Question 29:****A 5 V battery is connected to two 20 Î© resistors which are joined together in series. (a) Draw a circuit diagram to represent this. Add an arrow to indicate the direction of conventional current flow in the circuit. (b) What is the effective resistance of the two resistors ? (c) Calculate the current that flows from the battery. (d) What is the p.d. across each resistor ?**

**Solution :**

**Question 30:****The figure given below shows an electric circuit in which current flows from a 6 V battery through two resistors. (a) Are the resistors connected in series with each other or in parallel ? (b) For each resistor, state the p.d. across it. (c) The current flowing from the battery is shared between the two resistors. Which resistor will have bigger share of the current ? (d) Calculate the effective resistance of the two resistors. (e) Calculate the current that flows from the battery.**

**Solution :**

V = 6V. R_{1 }= 2ohms. R_{2} = 3ohms

(a) Resistors are connected in parallel

(b) p.d. across each resistor is same and is equal to 6V.

(c) 2 ohms resistance have bigger share of current because of its lower resistance.

(d) Effective resistance = R

1/R = 1/2+1/3

1/R = S/6

R = 1.2ohms

(e) Current flowing through battery, l = V/R = 6/1.2 = 5amps

**Question 31:****A 4 Î© coil and a 2 Î© coil are connected in parallel. What is their combined resistance ? A total current of 3 A passes through the coils. What current passes through the 2 Î© coil ?**

**Solution : **40 and 2Î© coil are connected in parallel. Combined resistance is R

**Question 32:****(a) With the help of a circuit diagram, deduce the equivalent resistance of two resistances connected in series. (b) Two resistances are connected in series as shown in the diagram **

**(i) What is the current through the 5 ohm resistance ? (ii) What is the current through R ? (iii) What is the value of R ? (iv) What is the value of V ?**

**Solution :**

(a) Fig shows two resistances R_{1} and R_{2} connected in series with a battery of V volts.

Let the p.d. across R_{1} is V_{1} and the p.d. across R_{2} is V_{2}.

S.t. V = V_{1} + V_{2} ....... (1)

Let the equivalent resistance be R and current flowing through whole circuit is I.

By Ohm's law,

V/I = R

V = I x R ---------(2)

Applying Ohm's law to both R_{1} end R_{2}

V_{1} = I x R_{2} --------(3)

V_{2} = I X R_{2} ----- â€”(4)

From eqs. (1), (2), (3) and (4), we get

I x R = I x R_{1}+ I x R_{2}

I x R = I x (R_{1} + R_{2})

R = R_{1} + R_{2}

(b)

(1) Current through 5Î© resisto r= 10/5 = 2A

Since 5Î© resistor and R are connected in series, so same current flows through them.

So, Current through R = 2A

(iii) V = IR

R = V/I = 6/2 = 3Î©

(iv) V = 10 + 6 = 16V

**Question 33:****(a) With the help of a diagram, derive the formula for the resultant resistance of three resistors connected in series. (b) For the circuit shown in the diagram given below :**

**Calculate : (i) the value of current through each resistor. (ii) the total current in the circuit. (iii) the total effective resistance of the circuit.**

**Solution :**

(a) Ng shows three reSistances R_{1}, R_{2} and R_{3} ecnnected in series with a battery of V volts.

Let the p.d. across R_{1}, R_{2} and R_{3} is V_{1}, V_{2} and V_{3} respectively.

s.t. V = V_{3} + V_{3} + V_{2} ----(1)

Let the equivalent resistance be R and arrent flowing through whole circuit is I.

By Ohm's law,

(ii) Total current in the cirait = 1.2+0.6+0.2 = 24

(iii) Effective resistance R is given as

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