Electric Charge and its Properties

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Which type of electric charge does a proton have?

Positive charge

What is the SI unit of charge?

Coulomb

What is the charge of an electron?

Negative charge

Which type of charge is repulsive when interacting with the same type of charge?

Positive charge Signup and view all the answers

Which type of charge is attractive when interacting with a different type of charge?

Negative charge Signup and view all the answers

Which type of material allows charge to flow easily?

Conductor Signup and view all the answers

Which type of material barely allows charge to flow?

Insulator Signup and view all the answers

What happens to the outermost electrons in a conductor?

They become free to move Signup and view all the answers

What is the simplest way to induce a charge on common materials?

Rubbing unlike materials together Signup and view all the answers

What happens when charge is moved from one object to another and then the objects are separated?

The charge is conserved Signup and view all the answers

Which process involves the transfer of charge between two objects made of unlike materials?

Induced polarization Signup and view all the answers

What is the result of rubbing two objects made of unlike materials together?

One object becomes positively charged and the other becomes negatively charged Signup and view all the answers

What is polarization?

The separation of charge within an object Signup and view all the answers

Which type of polarization occurs when one side of a molecule is more positive than the other?

Permanent polarization Signup and view all the answers

What is induced polarization?

The separation of charge within an object Signup and view all the answers

In a conductor, where do opposite charges accumulate when induced polarization occurs?

At the ends of the conductor Signup and view all the answers

In an insulator, where do charges accumulate when induced polarization occurs?

Nowhere, charges do not accumulate in an insulator Signup and view all the answers

Which type of polarization is shown in the figure for both a conductor and an insulator?

Induced polarization Signup and view all the answers

What is the overall charge of an object that is polarized?

Neutral Signup and view all the answers

What happens to the total charge during the process of rubbing two objects made of unlike materials together?

The total charge remains the same Signup and view all the answers

Which of the following is true about the electrical signal generated at the sinoatrial (SA node) of the heart?

It causes the contraction of the atria Signup and view all the answers

What is the role of the atrio-ventricular (AV) node in the heart?

To delay the contraction of the ventricles after the contraction of the atria Signup and view all the answers

What is the normal sinus rhythm of the heart?

A heart rate of 60-100 beats/min Signup and view all the answers

What is the function of an electrocardiogram (ECG)?

To detect abnormal heart rhythms Signup and view all the answers

What does the P wave in an electrocardiogram represent?

The depolarization of the atria Signup and view all the answers

What does the QRS complex in an electrocardiogram represent?

The depolarization of the ventricles Signup and view all the answers

What does the T wave in an electrocardiogram represent?

The repolarization of the ventricles Signup and view all the answers

What is the SI unit of capacitance?

Farad (F) Signup and view all the answers

What factors affect the capacitance of a capacitor?

The dielectric constant Signup and view all the answers

What is the capacitance of 1 cm2 of membrane with a dielectric constant of 8 and a thickness of 10-8 m?

0.708 μF Signup and view all the answers

According to Coulomb's law, the force between two electric charges is directly proportional to the product of the charges and inversely proportional to their separation squared.

True Signup and view all the answers

What is the formula for calculating the electric force between two charges q1 and q2, separated by a distance r?

F = k * q1 * q2 / r Signup and view all the answers

If two charges have opposite signs, the electric force between them is

attractive Signup and view all the answers

If two charges have the same signs, the electric force between them is

repulsive Signup and view all the answers

What is the value of the constant of proportionality (k) in Coulomb's law?

9 × 10^9 N m^2 C^-2 Signup and view all the answers

In the example given, what are the magnitudes of the two charges (q1 and q2)?

4 μC and 3 μC Signup and view all the answers

What is the distance separating the two charges in the example given?

1 m Signup and view all the answers

What is the magnitude of the electric force acting on q2 in the example given?

0.108 N Signup and view all the answers

What is the direction of the electric force acting on q2 in the example given?

East (+x) Signup and view all the answers

How would the answer change if q2 in the example given is negative?

The magnitude of the force would decrease Signup and view all the answers

Which symbol is used to represent electric current?

I Signup and view all the answers

What is the SI unit of electric current?

Ampere (A) Signup and view all the answers

What is the formula for electric resistance according to Ohm's law?

𝑹 = 𝑽/𝑰 Signup and view all the answers

What is the opposition to the flow of electrical current through an object called?

Resistance Signup and view all the answers

In the example given, what is the electric resistance if the potential difference is 20 V and the current is 4 A?

5 Ω Signup and view all the answers

What is the formula for calculating electric charge?

𝑸 = 𝑰 × 𝑽 Signup and view all the answers

In the example given, how many electric charges pass through the conducting wire in a minute if the current is 4 A?

240 C Signup and view all the answers

What are materials called that do not obey Ohm's law?

Non-Ohmic Signup and view all the answers

What are materials called for which the potential difference and current are directly proportional?

Ohmic Signup and view all the answers

What is the capacitance of the cell membrane mentioned in the text?

10-2 Fm-2 Signup and view all the answers

Which of the following is true about the resting membrane potential of a nerve cell?

The resting membrane potential is on the order of -70 to -90 mV Signup and view all the answers

What happens to the cell membrane permeability during an action potential?

It decreases suddenly to sodium and gradually to potassium Signup and view all the answers

What is the approximate duration of an action potential?

0.3 ms Signup and view all the answers

What is the shape and peak size of an action potential dependent on?

The strength of the above-threshold stimulus Signup and view all the answers

What is the purpose of the sodium-potassium pump in a nerve cell?

To actively pump sodium out and potassium in Signup and view all the answers

How long does it take for the sodium-potassium pump to restore the ions in a nerve cell?

50 ms Signup and view all the answers

What happens to the potential difference across the capacitors in an axon when a small stimulus is applied?

It gradually changes Signup and view all the answers

What happens when a stimulus above the threshold level is applied to an axon?

A current pulse associated with active potential is produced Signup and view all the answers

What is the signal conduction velocity in a nerve axon directly proportional to?

Axon's diameter Signup and view all the answers

What is the signal conduction velocity in a nerve axon inversely proportional to?

An axial resistance along the axon Signup and view all the answers

Study Notes

Electric Charge and Materials

A proton has a positive electric charge.
The SI unit of charge is the coulomb (C).
An electron has a negative electric charge.

Charge Interaction and Materials

Like charges repel each other.
Opposite charges attract each other.
Conductors are materials that allow charge to flow easily.
Insulators are materials that barely allow charge to flow.

Inducing Charge and Polarization

Inducing a charge on common materials can be done by rubbing them against other materials.
When charge is moved from one object to another and the objects are separated, the process is called charging by friction.
The transfer of charge between two objects made of unlike materials is called triboelectric charging.
When two objects are rubbed together, charge is transferred, resulting in one object becoming positively charged and the other becoming negatively charged.
Polarization is the process of creating a temporary or permanent electric dipole in a material.
When one side of a molecule is more positive than the other, it is called permanent polarization.
Induced polarization occurs when a material is placed in an electric field, causing the molecules to align.

Charge Accumulation and Conductors

In a conductor, opposite charges accumulate on the surface when induced polarization occurs.
In an insulator, charges accumulate inside the material when induced polarization occurs.
The overall charge of an object that is polarized is zero.

Electrophysiology

The sinoatrial (SA) node in the heart generates an electrical signal that regulates the heartbeat.
The atrio-ventricular (AV) node in the heart relays the signal from the SA node to the ventricles.
The normal sinus rhythm of the heart is around 60-100 beats per minute.
An electrocardiogram (ECG) measures the electrical activity of the heart.
The P wave in an ECG represents the atrial contraction.
The QRS complex in an ECG represents the ventricular contraction.
The T wave in an ECG represents the ventricular recovery.

Capacitance and Electric Force

The SI unit of capacitance is the farad (F).
The capacitance of a capacitor is affected by the dielectric constant, thickness of the dielectric, and surface area of the plates.
According to Coulomb's law, the electric force between two charges is directly proportional to the product of the charges and inversely proportional to their separation squared.

Electric Current and Resistance

The symbol for electric current is I, and the SI unit is the ampere (A).
Electric resistance is the opposition to the flow of electrical current through an object.
The formula for electric resistance according to Ohm's law is R = V/I.
Materials that do not obey Ohm's law are called non-ohmic materials.
Materials that obey Ohm's law are called ohmic materials.

Nerve Cells and Action Potentials

The capacitance of the cell membrane is around 1 μF/cm².
The resting membrane potential of a nerve cell is around -70 mV.
During an action potential, the cell membrane permeability changes.
The duration of an action potential is around 1-2 ms.
The shape and peak size of an action potential are dependent on the ion channels and pumps.
The sodium-potassium pump restores the ions in a nerve cell after an action potential.
It takes around 1-2 minutes for the sodium-potassium pump to restore the ions.
When a stimulus above the threshold level is applied to an axon, an action potential is generated.
The signal conduction velocity in a nerve axon is directly proportional to the diameter of the axon and inversely proportional to the axon's length.

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