A transformer core is laminated to

The efficiency of a transformer will be maximum when

A transformer transforms

Two transformers operating in parallel will share the load depending upon their

The path of the magnetic flux in transforme should have

The full-load copper loss of a transformer is 1600 W. At half-load, the copper loss will be

Which winding of the transformer has less cross-sectional area

Open circuit test on transformer is conducted to determine

Short circuit test on transformer is conducted to determine

The hum in a transformer is mainly attributed to

A transformer is working at its maximum efficiency. Its iron loss is 1 kW. Its copper loss will be

A transformer is working at its full load and its efficiency is also maximum. Its iron loss is 1 kW, its copper loss at half load will be

The working principle of a transformer is

The output current corresponding to the maximum efficiency for a transformer having core loss of 200 W and equivalent resistance referred to secondary of 0.5 ohms is

For parallel operation of two single phase transformers the essential condition is that they should have the same

Transformer is used to change the values of

Electric power is transferred from one coil to the other coil in a transformer

At every instant the direction of secondary current in a transformer must be such as to oppose any change in flux. This in accordance with

If in a transformer the secondary turns are doubled and at the same time the primary voltage is reduced by half, then the secondary voltage will

Which is the common method of cooling a power transformer?

The transformer oil used in transformers provides

Three number of 10:1 transformers are connected in Y-Delta to supply a load at 230 V. The supply voltage of this transformer must be

A transformer has a turns ratio of 1 to 10 and a resistance of 5000 ohms is connected across the secondary terminals, the resistance offered to a current flowing in the primary will be

Three units of 1.5 transformers are connected in Delta-Wye to supply a 3-phase load from a 400 V, 3-phase source. The line voltage on the load side is

A transformer is working at its full load and its efficiency is also maximum. Its iron loss is 1000 W, its copper loss at half load will be

In power transformers the tappings are provided on

Three single-phase transformer, each with a 10 KVA rating are connected in a closed delta arrangement. If one transformer is taken out capacity of the system will be

When 440/220 V transformer is connected to 400 V d.c supply

A transformer has a core loss of 64 W and copper loss of 144 W, when it is carrying 20% overload current. The load at which this transformer will operate at the maximum efficiency is

If 500-kVA, 400 Hz transformer is operated at 100 Hz, its kVA rating is

The efficiency in transformer is maximum at

For 100% efficient transformer if the number of turns in the primary and secondary are 1000 and 100 respectively and the input to the transformer is 1000 W, the power output will be

No-load test on a transformer is carried out to determine

The main purpose of performing open-circuit test at rated voltage is to measure

The short-circuit test in a transformer is use to determine

When a 400-Hz transformer is operated at 50-Hz, its kVA rating is

The iron-losses of a transformer can be calculated by knowing the weights of

The output current corresponding to the maximum efficiency for a transformer having core loss of 100 W and equivalent resistance referred to secondary of 0.25 ohms is

If a current transformer has a ratio of 100:5 and an ammeter connected to its secondary reads 2.5 A, the actual line current is

For supplying a balanced 3-phase load of 40-kVA rating of each transformer in V-V bank should be

The percentage over-loading of two 20-kVA transformers when supplying a balanced 3-phase load of 40kVA in V-V bank is

For small power transformers, it is preferable to use

For large power transformers, it is preferable to use

Eddy current loss in a tranformer depends on

The short-circuit test on a transformer is conducted to obtain

Transformer -core laminations are made of

The essential condition for parallel operation of two single-phase transformers is that they should have same

Part of the transformer which is most subject to damage from overheating is

In general, the most important point to keep under constant watch during the operation of a transformers is its

In a 10: 1 step-down 2200/220-V transformers, taps are changed to reduce the number of primary turn by 5%. The secondary voltage will nearly be

The color of fresh dielectric oil for a transformer is

A 10 kVA, 230/1000V single transformer is fed from a 230 V supply. The voltage across the load will be

A 5 kVA 200/100 V single phase transformer delivers 50 A at rated voltage. The input current will be