The following measurements are obtained on a single phase load: $$V = 220 V$$ $$ \pm $$$$1$$%. $${\rm I}$$$$= 5.0$$ $$A$$ $$ \pm \,1$$% and $$W=555$$ $$W$$ $$ \pm \,2$$%. If the power factor is calculated using these measurements, the worst case error in the calculated power factor in percent is _________. (Give answer up to one decimal place.)

The load shown in the figure is supplied by a $$400$$ $$V$$ (line-to-line) $$3$$-phase source ($$RYB$$ sequence). The load is balanced and inductive, drawing $$3464$$ $$VA.$$ When the switch $$S$$ is in position $$N$$, the three watt-meters $${W_1},\,{W_2}$$ and $${W_3}$$ read $$577.35$$ $$W$$ each. If the switch is moved to position $$Y,$$ the readings of the watt-meters in watts will be:

The slope and level detector circuit in a CRO has a delay of 100 ns. The start-stop sweep generator has a response time of 50 ns. In order to display correctly, a delay line of

A 220 V DC series motor runs drawing a current of 30 A from the supply. Armature and field circuit resistances are 0.4 Ω and 0.1 Ω respectively. The load torque varies as the square of the speed. The flux in the motor may be taken as being proportional to the armature current. To reduce the speed of the motor by 50% the resistance in ohms that should be added in series with the armature is _________.