Power and Energy

Question 1

Define Energy.

Answer 1

The abiity to do work. Joules (J) in W

Question 2

Define power.

Answer 2

• Rate of energy transfer. Watts (W) in P
• P=W/t
• P=VI
• P=I^2R
• P=V^2/R

Question 3

What is power rating of resistor?

Answer 3

• The maximum amount of power a resistor can dissipate without being damaged is called a power rating.
• The larger the resistor size, the higher the power rating
• E.g 1/8W , 1/4W, 1/2W, 1W

Question 4

How is a voltage drop caused in terms of energy?

Answer 4

• When the electron current passes through a resistive material, such as a resistor
• The free electrons collide with ions in the resistive material,
• The free electrons are scattered in random motion and do not move in the well-aligned manner as inside a conductor
• This causes conversion of electrical energy to heat energy.
• The lost of electrical energy results in a voltage drop across the resistive material

Question 5

What is a perfect conductor?

Answer 5

• A perfect conductor has zero resistivity and consumes no power.
• The potential difference between any two points in a piece
  of perfect conductor is zero (zero voltage drop)