An electric pencil sharpener rated 24U mW o V is connected t

An electric pencil sharpener rated 24U mW, o V is connected to a 9-V battery as shown in Fig. 2.138. Calculate the value of the series-dropping resistor R_z needed to power the sharpener.

Solution

load active power=9m watts

load voltage =6 volts

source voltage=9 volts

so, the drop across resistor=9-6=3 volts.

load active power =9*10^-3=6*i*1

load current (i)=(9*10^-3)/6=1.5*10^-3 amps.

so, resistor RX= voltage drop/load current=3/(1.5*10^-3)=2kohms.