Advertisements
Advertisements
प्रश्न
A 200V/120V step-down transformer of 90% efficiency is connected to an induction stove of resistance 40 Ω. Find the current drawn by the primary of the transformer.
Advertisements
उत्तर
Given data:
Vp = 200 V
Vs = 120 V
η = 90% = `90/100` = 0.9
`η = "output power"/"input power"`
`therefore 0.9 = ("V"_"S""I"_"S")/("V"_"p""I"_"p")`
`therefore "V"_"S" = "I"_"S""R"_"S"`
`"I"_"S" = "V"_"S"/"R"_"S" = 120/40` = 3A
∴ 0.9 = `(120 xx 3)/(200 xx "I"_"p")`
`"I"_"p" = (120 xx 3)/(200 xx 0.9) = (120 xx 3)/(20 xx 9)`
`"I"_"p"` = 2 A
APPEARS IN
संबंधित प्रश्न
The teachers of Geeta’s school took the students on a study trip to a power generating station, located nearly 200 km away from the city. The teacher explained that electrical energy is transmitted over such a long distance to their city, in the form of alternating current (ac) raised to a high voltage. At the receiving end in the city, the voltage is reduced to operate the devices. As a result, the power loss is reduced. Geeta listened to the teacher and asked questions about how the ac is converted to a higher or lower voltage.
1) Name the device used to change the alternating voltage to a higher or lower value. State one cause for power dissipation in this device.
2) Explain with an example, how power loss is reduced if the energy is transmitted over long distances as an alternating current rather than a direct current.
3) Write two values each shown by the teachers and Geeta.
Name the phenomenon ?
The transformer is used in ______ current circuits.
What is the turns ratio i.e., transformer ratio, ns: np, in an ideal transformer which in-creases ac voltage from 220 V to 33000 V?
Applying e.m. f to primary coil is 210 V. If the number of turns in primary coil is 200 turns and that of in secondary coil is 20 turns, then find out the output voltage. Name the type of transformer.
The output power in step-up transformer used in practice is ______.
Read the following paragraph and answer the question:
Long distance power transmissions
The large-scale transmission and distribution of electrical energy over long distances is done with the use of transformers. The voltage output of the generator is stepped up. It is then transmitted over long distances to an area sub-station near the consumers. There the voltage is stepped down. It is further stepped down at distributing sub-stations and utility poles before a power supply of 240 V reaches our homes.
Which of the following statement is true?
The primary coil of a transformer has 800 turns and the secondary coil has 8 turns. It is connected to a 220 V ac supply. What will be the output voltage?
A transformer is used ______
For an LCR circuit, the power transferred from the driving source to the driven oscillator is P = I2Z cos φ.
- Here, the power factor cos φ ≥ 0, P ≥ 0.
- The driving force can give no energy to the oscillator (P = 0) in some cases.
- The driving force cannot syphon out (P < 0) the energy out of oscillator.
- The driving force can take away energy out of the oscillator.
