# The Ta/Ia graph of a d.c. series motor is a?

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The Ta/Ia graph of a d.c. series motor is a?

The Ta/Ia graph of a d.c. series motor is a parabola upto full-load and a straight line at overloads.

## Related questions

The d.c. series motor should never be switched on at no load because?

The widely used series-parallel system of speed control of d.c. series motors in traction work gives a speed range of about (a) 1 : 2 (b) 1 : 3 (c) 1 : 4 (d) 1 : 6

The purpose of inserting external resistance at the time of starting a d.c. motor is to (a) increase the starting torque. (b) increase the armature flux. (c) reduce the starting current. (d) reduce the armature flux.

The function of carbon brush and commutator arrangement in a d.c. motor is (a) to produce unidirectional torque. (b) to produce unidirectional current in the armature. (c) to help in changing the direction of rotation. (d) to reduce sparking.

The shaft torque of a d.c. motor is less than its armature torque because of .......... losses.

Under constant load conditions, the speed of a d.c. motor is affected by?

The induced e.m.f. in the armature conductors of a d.c. motor is?

The mechanical power developed by the armature of a d.c. motor is equal to?

The Eb/V ratio of a d.c. motor is an indication of its?

The normal value of the armature resistance of a d.c. motor is?

In a d.c. motor, unidirectional torque is produced with the help of

D.C. motor is to a drive a load which is almost nil for certain part of the load cycle and peak value for short duration. We will select the?

D.C. motor is to drive a load which has certain minimum value for most of the time and some peak value for short duration. We will select the?

A d.c. shunt motor runs at no load speed of 1140 r.p.m. At full load armature reaction weakens the main flux by 5%. Whereas the armature circuit voltage drops by 10%. The full load speed of the motor is (a) 1200 r.p.m. (b) 1080 r.p.m. (c) 1040 r.p.m. (d) 1000 r.p.m.

With the increase in load on a d.c. shunt motor, speed of the motor (a) increases proportionately (b) remains constant (c) increase slightly (d) reduces slightly

If the pole flux of a d.c. motor approaches zero, its speed will?

If the load current and flux of a d.c. motor are held constant and voltage applied across its armature is increased by 10 per cent, its speed will?

The current drawn by a 120 - V d.c. motor of armature resistance 0.5 Ω and back e.m.f. 110 V is .......... ampere.

The counter e.m.f. of a d.c. motor?

If a d.c. motor is disconnected from the source and armature circuit is short circuited through a suitable resistance, the process is called (a) regenerative breaking (b) rheostatic breaking (c) dynamic breaking (d) no breaking is possible

The chief advantage of Ward-Leonard system D.C. motor speed control is that is  1. Can be used even for small motors 2. has high overall efficiency at all speeds 3. Gives smooth, sensitive and wide speed control 4. Uses a flywheel to reduce fluctuations in power demand

A d.c. motor develops a torque of 200 N-m at 25 rps. At 20 rps it will develop a torque of .......... N-m.

A d.c. shunt motor is found suitable to drive fans because they require?

If load on a d.c. shunt motor is increased, its speed is decreased due primarily to?

In a d.c. motor, the mechanical output power actually comes from?

A d.c. motor can be looked upon as d.c. generator with the power flow?

In a d.c. series motor, the torque developed is 20 Nm at 10A. If the load current is doubled, the new torque will be : -  a) 60 Nm b) 45 Nm c) 80 Nm d) 100 Nm

A separately excited d.c. motor fed from single phase full converter with firing angle 60° runs at 1000 r.p.m. If motor is connected to single phase semiconverter with the same firing angle of 60°, it would run at (a) 2000 rpm (b) 1850 rpm (c) 1500 rpm (d) 1000 rpm

A shunt d.c. motor works on a.c. mains?

A series R-L circuit is suddenly connected to d.c. voltage source of V volts. The current in this series circuit, just after the switch is closed, is equal to (1) Zero (2) V/L (3) V/C (4) V.L/C

Neglecting saturation, if current taken by a series motor is increased from 10 A to 12 A, the percentage increase in its torque is ........ percent

The maximum torque of d.c. motors is limited by?

A dc series motor driving and electric train faces a constant power load. It is running at rated speed and rated voltage. If the speed has to be brought down to 0.25 p.u. the supply voltage has to be approximately brought down to  (A) 0.75 p.u (B) 0.5 p.u (C) 0.25 p.u (D) 0.125 p.u