(1) Cells, EMF, terminal voltage & internal resistance | Electric current | Physics | Khan Academy

What does EMF stand for in a battery context?

Electromotive Force.

What is the definition of EMF?

A measure of energy transfer; specifically, the energy transferred by the battery per coulomb.

How much energy does a 9V battery transfer per coulomb?

9 joules of energy per coulomb.

What happens to terminal voltage as more current is drawn from a battery?

The terminal voltage decreases.

What causes the decrease in terminal voltage when more bulbs are added in parallel?

Increased current draw leads to increased internal resistance loss, resulting in heat dissipation.

What is internal resistance?

Resistance within a battery that opposes the flow of charge, causing energy loss as heat.

What is terminal voltage?

The net energy gained by a coulomb as it moves through the battery after accounting for energy lost as heat.

How can we express the relationship between terminal voltage (VT), EMF (E), current (I), and internal resistance (R)?

VT = E - I * R.

What happens to terminal voltage when charges move faster through the battery?

The terminal voltage decreases due to increased heat loss.

Why does terminal voltage equal EMF when current is zero?

No heat is lost when there is no current, so all EMF is available as terminal voltage.

What is the effect of adding more resistors (bulbs) in parallel on the effective resistance?

The effective resistance decreases.

What is the relationship between increased current draw and heat loss in a battery?

Increased current draw increases heat loss due to internal resistance.

If a 9V battery dissipates 2 joules as heat per coulomb, what is the terminal voltage?

7 volts.

What happens to energy transferred to a charge in a battery due to internal resistance?

Some energy is dissipated as heat, reducing the energy available to the charge.

What analogy is used to explain how a battery transfers energy to a charge?

Like a parent pushing a child up a slide, transferring energy to the child.