Question

to study the factor on which the self inductance of a coil depends by observing the effect of this coil when put in series with a resistor in a circuit fed up by an a.c. source of adjustable frequency. plzzz provide the observation table for the same.

Answer 1

 

Procedure

B6a4e all connections as shown in circuit diagra$!BSwitch on the !"! supply and adjust the constant current in the circuit by using the variable resistor ('0) (let fre#uency of source is +/ A9 and voltage is +=)!B'ecord the current in !"! a$$eter and see the brightness of bulb!B&ow, put the soft iron rod inside the inductor core and record the current in !"! a$$eter and again chec4 the brightness of bulb!  The current and brightness both decreases!B&ow, switch o the supply and decrease the fre#uency of !"! source (say ;/ A9)!Bgain switch on the supply and adjust the current in circuit at sa$e constant voltage += by using the rheostat! &ote the currentin a$$eter and brightness of bulb! The current and brightness both will increases!

 

Bgain insert the iron in the core of coil and note the current and brightness! The current and brightness both decreases!B'epeat the steps ;, + and 1 for dierent fre#uency of !"! source(say / A9,*/ A9 and ./ A9)!

-bservations

B >east "ount rror? !BEero error of a$$eter? !B'ange of a$$eter? !S &o!Jre#uency of applied voltage(A9)"urrent in a$$eter without iron rodin coil ()"urrent in a$$eter with iron rod in coil ()0!+/.!;/*!/!*/;!./

'esult

 

BThe current in the circuit decrease on inserting the iron rod in the core of coil at constant fre#uency of applied voltage and brightness of bulb decreases and vice%versa!BThe current in the circuit increases on decreasing the fre#uency of applied voltage and vice%versa! Therefore, the brightness of bulb increases!

Precautions

BThe coil should have large nu$ber of turns!B"urrent should be passed for a s$all ti$e to avoid the heating eect!BThere should not be paralla5 in ta4ing the reading of a$$eter!

Sources of rror

BThe resistance of circuit $ay increases slightly due to heating eect of current!BThere $ay be eddy current in soft iron coil!

Answer 2

Circuit diagram and observation table are attached

Aim:

To study the factor on which the self inductance of a coil depends by observing the effect of this coil when put in series with a resistor in a circuit fed up by an a.c. source of adjustable frequency.

Theory:

The self inductance of a coil is L =(μ₀μrN²A)/l

When an Inductor is connected in series with a resistor (bulb) with a variable source of frequency, then current flowing in the bulb is

Irms = Erms/Z

here Z =√(R2 )+ ω2 L2 = Impedance of the a.c. circuit

The brightness of bulb i.e. heat generated in bulb is

H = Irms2Zt

P = H/t = Irms2Z

P = Irms2(√R2 + ω2 L2)

Requirements

• a.c. source of adjustable frequency
• (10V) a.c. ammeter of suitable range rheostat
• A coil of large turns
• a soft iron rod
• one way key
• an electrical bulb
• connecting wires

Circuit:

circuit diagram

Steps involved:

1. Switch on the A.C. supply and adjust the constant current in the circuit by using the variable resistor (R1) (for example take voltage 10V and frequency of source 50 Hz).

2. Note the current in a.c. ammeter and see the brightness of bulb.

3. Now, put the soft iron rod inside the Inductor core and note the current in a.c. ammeter and see the brightness of bulb. (The current and brightness both decreases)

4. Now, switch off the supply and decrease the frequency of a.c. source.

5. Again switch on the supply and adjust the current in circuit at same constant voltage 10V by using the rheostat. Note the current in ammeter and brightness of bulb. The current and brightness both will increases.

6. Again insert the iron in the core of coil and note the current and brightness. The current and brightness both decreases.

7. Repeat the steps 4, 5 and 6 for different frequency of a.c. source.

Observation:

observation table

Result:

• the current decreases on inserting iron rod at constant frequency of voltage.
• the current increases on decreasing frequency of voltage

Precautions:

Current should be passed for a small time to avoid the heating effect.

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