161 164

161. Two bulbs of 100w and 40w respectively connected in series across a 230v supply which bulb will glow bright and why? 

Since two bulbs are in series they will get equal amount of electrical current but as the supply voltage is constant across the bulb (P=V^2/R).So the resistance of 40W bulb is greater and 
voltage across 40W is more (V=IR) so 40W bulb will glow brighter. 

162. Why temperature rise is conducted in bus bars and isolators? 

Bus bars and isolators are rated for continuous power flow that means they carry heavy currents which rises their temperature. So it is necessary to test this devices for temperature rise. 

163. What is a System? 

When a number of elements or components are connected in a sequence to perform a specific function, the group of elements that all constitute a System.

164. What is Control System? 

In a System the output and inputs are interrelated in such a manner that the output quantity or variable is controlled by input quantity, then such a system is called Control System.