Electromotive Force

Arrhythmia

A condition occurring when the electrical signals that regulate the heart’s rhythm malfunction; resulting in heart beating too fast or irregularly

Implantable Cardioverter Defibrillator (ICD)

Surgically provided to people with the life threatening arrhythmia

Esther Sans Takeuchi

American Chemical engineer to come up with ICDs with increased longevities

Lithium-silver vanadium oxide batteries

What increased the longevity and power output of the ICDs

Alessandro Volta

Italian physicist who coined the term ‘electromotive force’

Voltaic pile

The very first invented battery

one terminal at a higher electric potential than the other terminal, acting as a source of current in a circuit.

A source of emf maintains

there is no net flow of charge within the emf

When the emf source is not connected to the lamp then…

electrons must be moved from the positive terminal to the negative terminal

In order for the emf source to maintain the potential difference between the two terminals….

charge pump

The emf source acts as ___________

Increases the potential energy of the charges and, therefore, the electrical potential of the charges.

What does the emf source moving the negative charges from the positive terminal to negative terminal to maintain the potential difference do?

Work, energy, chemical reactions

____ must be done on the negative charges for them to be moved to the negative terminal. This requires ______, which comes from __________________ in the battery.

ε = dW/dq

Formula emf when there is no current flowing

1 V = 1J/C

Unit for emf and its derivation

Terminal voltage of a battery

Voltage measured across the terminals of the battery.

Ideal battery

An emf source that maintains a constant terminal voltage, independent of the current between the two terminals.

Has no internal resistance and its terminal voltage is equal to the emf of the battery

chemical

The combination of _________ and the makeup of the terminals in a battery determine its emf.

Lead acid battery

The battery used in cars and other vehicles

Anode

(1)

Cathode

(2)

Sulfuric acid

(3)

Also, is considered as the electrolyte of the system

Both the plates immersed in this chemical

This chemical conducts the charge as well as participates in the chemical reaction

Lead Oxide

(4)

Lead

(5)

Positive terminal

The terminal of the cell inside the lead acid battery that is connected to the lead oxide plate

Negative terminal

The terminal of the cell inside the lead acid battery that is connected to the lead plate

anode, cathode, chemical reactions, closed-circuit, supply, cathode

In the lead acid battery, two electrons are forced onto the _____ of the cell and two electrons are removed from the _______ of the cell.

This is done by the _________________. It requires the circuit to be a ______________ because this will ______ the electrons to the _______ in the first place.

Lithium-ion batteries

Other types of batteries that are found in many devices.

Function in the same general way as lead-acid batteries but utilize different chemicals

graphite, silicon-based material, metallic lithium

In many cases anode is composed of ________, ______________________, or ________________.

Lithium oxide compound, manganese, cobalt, lithium salt.

In many cases cathode is often composed of ________, which may also contain _________, __________, or other materials.

And the electrolyte is usually a type of ___________.

Internal resistance

The amount of resistance to the flow of current within the voltage source.

Depleted battery

Refers to a battery that has lost its charge and no longer can be used.

depleted

Internal resistance increases as a battery is ________

Oxidation of the plates or the reduction of the acidity of the electrolyte

Two reasons that can make the battery depleted.

Magnitude and direction of the current in the battery, its temperature, and its history.

Three things on which the internal resistance may depend on.

Rechargeable nickel-cadmium cells

It’s internal resistance depends on how many times and how deeply they have been depleted

Idealized emf source and an internal resistance

Two things that is consisted inside the simple model of a battery.

V(terminal) = ε - Ir

Formula for the terminal voltage of the battery.

decreases, increases

The terminal voltage _________ as the current _________ due to the potential drop I*r of the internal resistance.

Volts

(y)

Battery

(iii)

ΔV = I*r [The potential drop across the internal resistor]

(iv)

ε - I*r [That’s what the terminal voltage of the battery is]

(ii)

ΔV = I*R = ε - I*r [Potential drop across the load resistor, which is equal to the terminal voltage across the battery]

(v)

I = ε/(r + R)

Formula to find the current through the load resistor

Indicates that smaller the internal resistance, the greater will be the current supplied by the voltage source to its load resistor.

ε [Done by the chemical reactions doing the work on the charges]

(i)

Yes, it is true

Is it true that the internal resistance of a rechargeable battery increases as the number of times the battery is recharged increases.

Its terminal voltage will decrease and the battery may overheat due to the increased power dissipated by the internal resistance.

The two effects that the increased resistance may have on the battery.

Battery testers

A device that measures the terminal voltage under a load to determine condition of a battery.

Provides a measurement of the internal resistance of the battery

Uses small load resistors to intentionally draw current to determine whether the terminal potential drops below an acceptable level.

weak, low terminal voltage

If the internal resistance of the battery is high, then the battery is ____, as evidenced by its ____________________.

Battery charger

Devices that reverses the normal direction of the current through a battery, reversing its chemical reaction and replenishing its chemical potential.

To do all this its voltage output must be greater than the emf of the battery. Causing the terminal voltage of the battery to be greater than its emf, as I is now negative

Used routinely in cars and in batteries for small electrical appliances and electronic devices.