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प्रश्न
A 60 W load is connected to the secondary of a transformer whose primary draws line voltage. If a current of 0.54 A flows in the load, what is the current in the primary coil? Comment on the type of transformer being used.
उत्तर
PS = 60 W, IS = 0.54 A, IP = ?
PS = VSIS
60 = VS × 0.54
`60/0.54` = VS
VS = 111.10 Volt
In multiple of 11
VS = 110 Volt
Ratio factor of transformer 'r` = output voltage/input voltage
`r = V_S/V_P` ⇒ `r = (110 "Volt")/(220 "Volt") = 1/2`
Or r < 1, so transformer is step down transformer.
In transformer, output power = input power.
ISVS = IPVP
`I_P = (I_SV_S)/V_P = (0.54 xx 110)/220`
IP = 0.27 ampere
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संबंधित प्रश्न
A group of students while coming from the school noticed a box marked "Danger H.T. 2200 V" at a substation in the main street. They did not understand the utility of a such a high voltage, while they argued, the supply was only 220 V. They asked their teacher this question the next day. The teacher thought it to be an important question and therefore explained to the whole class.
Answer the following questions:
(i) What device is used to bring the high voltage down to low voltage of a.c. current and what is the principle of its working ?
(ii) Is it possible to use this device for bringing down the high dc voltage to the low voltage? Explain
(iii) Write the values displayed by the students and the teacher.
Explain the significance of Lenz’s law to show the conservation of energy in electromagnetic induction.
State the principle of working of a transformer. Can a transformer be used to step up or step down a d.c. voltage? Justify your answer.
The power supply to the primary coil of a transformer is 200 W. Find
(i) Current in primary coil if the e.m.f. supply to it is equal to 220V.
(ii) The number of turns in the primary coil is equal to 80 and that in secondary is 800. What is the transformation ratio?
(iii) Name the type of transformer.
(iv) What will be the output voltage?
(v) What is the current in the secondary coil for an ideal transformer?
(vi) What is the output power?
(vii) Is output and input power equal?
(viii) Compare the current flowing in a secondary coil and in a primary coil.
State the mathematical relation between a number of turns in the primary coil to a secondary coil in the step-up transformer.
For an ideal step-down transformer, the quantity which is constant for both the coils is ______.
A transformer is essentially an a.c. device. It cannot work on d.c. It changes alternating voltages or currents. It does not affect the frequency of a.c. It is based on the phenomenon of mutual induction. A transformer essentially consists of two coils of insulated copper wire having different numbers of turns and wound on the same soft iron core.
The number of turns in the primary and secondary coils of an ideal transformer is 2000 and 50 respectively. The primary coil is connected to a main supply of 120 V and secondary coil is connected to a bulb of resistance 0.6 Ω.
The value of voltage across the secondary coil is ______.
The line that draws power supply to your house from street has ______.
- zero average current.
- 220 V average voltage.
- voltage and current out of phase by 90°.
- voltage and current possibly differing in phase `phi` such that `|phi| < pi/2`.
Explain why core of a transformer is always laminated.
