7.4 drift velocity

Question 1

What is needed for current to flow in a material

Answer 1

Suitable charge carriers must be present in the material

Question 2

What are examples of a charge carrier

Answer 2

Loosely bound electrons in metals or ions in electrolytes and gases

Question 3

What direction does an electric current usually flow

Answer 3

The direction in which a positive charge would move

Question 4

How would the charge carriers move if they were negative

Answer 4

The charge carriers would move in the opposite direction to the current

Question 5

How do electrons move in metallic conductors and with what kind of speed

Answer 5

The electrons move with random thermal motion at speeds approaching one-thousandth the speed of light

Question 6

What are electrons mainly responsible for in metals

Answer 6

The fact that they are good conductors of heat

Question 7

What is the process that causes electrons to drift

Answer 7

A potential difference is applied to a circuit, an electric field is created that exerts a force on the free electrons, causing them to drift in the direction of the force

Question 8

How do atoms end up with constant drift velocity and what does this mean for the current

Answer 8

Due to Newton’s second law, electrons would accelerate continuously but they collide with regularly spaced atoms in the crystal lattice. These atoms are effectively positive ions since the free electrons are detached from them. The collisions between the electrons and the positive ions cause an equal and opposite force to be exerted on the electrons. By newtons first law this causes the electrons to continue with constant drift velocity, which gives rise to a constant current