PAST PPDC (OLD)

The condition in Ohm’s Law is that:

• ratio V/I should be constant

• current should be proportional to voltage

• temperature must be constant

• temperature should vary

The resistance of carbon when its filament temperature is decreased

• increases

• decreases

• remains the same

• increase enormously

It was experimentally found by James Prescott Joules that the heat produced in a current carrying conductor is proportional to:

• the square of current

• square of resistance

• the current

• inversely proportional to time

The presence of electric current is made known by:

• flashing

• effects produced

• cracking

• electric shock

The resistance R1 and R2 are in parallel. The ratio of the value of resistance R1:R2 is 4:1. The currents in R1:R2 will be equal to:

• 1:4

• 1:1

• 4:1

• 4:4

Four resistances are connected in series such that R1>R2>R3>R4 and supplied by a 110V source. The least power consumption will be in:

• R1

• R2

• R3

• R4

Three resistances are connected in series with a 220V supply. If R2 becomes open-circuited, the reading of the voltmeter will:

• become 220V

• decrease slightly

• fall to zero

• increase slightly

What is the formula for Maximum Power Transfer or Pmax?

• V2/ 4R2

• V2 / 4R

• V2/ R

• V2/ 2R

In the case of delta-connected circuit, when one resistor is open, the power will be:

• unaltered

• reduced to 1/3

• reduced to 1/9

• reduced to 1/6

What will happen to the reactance of the capacitor when the capacitance is reduced by 25%?

• increase by 25%

• increase by 33%

• increase by 50%

• . increase by 75%