Electric Charges

Electric charges are fundamental properties of subatomic particles that can be positive or negative. Particles with the same charge repel each other, while particles with opposite charges attract each other.

Electric Forces

Electric forces are the forces that arise between two electric charges. Like charges experience repulsive forces, while opposite charges experience attractive forces. Coulomb's law is used to calculate the electric force between two charges.

Electric Fields

Electric fields are created by electric charges and surround them. The electric field at a point is defined as the force experienced by a positive test charge placed at that point. Electric fields can be calculated using Coulomb's law.

Electric Flux

Flux is the amount of electric field passing through a certain area. In the context of electric charges, flux is measured as the number of electric field lines crossing a specific surface. The electric field flux can be calculated by multiplying the electric field by the surface area and the cosine of the angle between the field and the surface.

Electric Potential

Electric potential at a point in an electric field is defined as the energy required to move a positive test charge from that point to an infinitely distant reference point without doing work. Electric potential is measured in volts. The potential difference between two points in an electric field can be used to calculate the energy given or gained by a charge when moving between those points.

Electric Potential Energy

Electric potential energy is the energy possessed by electric charges due to their relative positions in an electric field. Electric potential energy can be calculated by multiplying the electric potential at a point by the electric charge at that point.

Elektron berpindah ke tempat yang lebih kekurangan. Proses tersebut berlangsung hingga mencapai keseimbangan.

Formula

$$F = k \frac{q_{1} q_{2}}{r^{2}}$$

• F = force (Newton)
• k = Coulomb's constant (9 × 10⁹ Nm²/C²)
• q = charge (Coulomb)
• r = distance (meter)

Formula

$$F = k \frac{q}{r^{2}}$$

• F = force (Newton)
• k = Coulomb's constant (9 × 10⁹ Nm²/C²)
• q = charge (Coulomb)
• r = distance (meter)

What is flux?

Electric flux is a measurement of the number of electric field lines that pass through a specific area. Simply put, you can envision electric flux as a quantity of "lines" crossing a surface.

Apa itu fluks listrik?

Fluks listrik adalah ukuran seberapa banyak garis medan listrik yang melintasi suatu daerah tertentu. Secara sederhana, kamu dapat membayangkan fluks listrik sebagai sejumlah "garis" yang melintasi permukaan.

Electric flux (Φ) is calculated by multiplying the electric field (E) by the area of the surface that the field passes through (A) and by the cosine of the angle between the field direction and the surface normal (θ).

The mathematical formula to calculate electric flux is
Φ = E * A * cos(θ).

An important application of electric flux is found in Gauss's law in electrostatics. Gauss's law states that the electric flux leaving a closed surface is proportional to the net charge inside that surface. In other words, Gauss's law enables us to use electric flux to determine the charge enclosed within a closed surface.

Aplikasi penting fluks listrik adalah hukum Gauss dalam elektrostatika. Hukum Gauss menyatakan bahwa fluks listrik yang keluar dari suatu permukaan tertutup sebanding dengan muatan bersih di dalam permukaan tersebut. Dalam kata lain, hukum Gauss memungkinkan kita untuk menggunakan fluks listrik untuk menghitung muatan di dalam suatu permukaan tertutup.

Here are some examples of electric flux applications in the field of electronics:

1. Capacitors

2. Printed Circuit Boards (PCBs)

3. Electrostatic field analysis

4. Electrostatic Discharge (ESD) testing

5. Capacitive sensors

A particle physicist analyzes the results of her particle collider experiment. The analysis shows that a nucleus involved in the collision had a charge of 9.5 x 10^-19 C ± 0.2 x 10^-19 C. The magnitude of an electron's charge is e = 1.60 x 10^-19 C. About the validity of the experimental results, the particle physicist should … .

1. not be concerned, since the observed charge is greater than e
2. not be concerned, since the observed charge is a multiple of e
3. be concerned, since it is not possible to have an observed charge greater than 5e
4. be concerned, since the observed charge is not an integer multiple of e
5. be concerned, since the observed charge is lower than e

2. An object that is initially neutral will be positive when … .

1. object loses electrons
2. object loses proton
3. object gains protons
4. object gains additional neutrons
5. object gains additional protons and electrons

3. A researcher is analyzing a particle decay process. The data for one experiment shows a particle of charge -3e decaying to form two new particles. One of the new particles has a charge of -e.

The charge of the particle Q, is … .

1. -3e
2. -2e
3. -e
4. e
5. 2e

4. A metal block with a charge Q₁ = +3e sits near a metal ball with a charge Q₂ = -5e.

If the block is touched to the ball, the possible final charge on each object is … .

1. Q₁ = +4e, Q₂ = -4e
2. Q₁ = +1e, Q₂ = +1e
3. Q₁ = -1e, Q₂ = -1e
4. Q₁ = 0e, Q₂ = -3e
5. Q₁ = +2e, Q₂ = -2e

5. A metal cube and a metal cylinder both have the same negative charge -Q and are brought into contact to each other.

A correct choice describing the net movement of charges is … .

1. Electrons move from the cube to the cylinder
2. Protons move from the cube to the cylinder
3. Electrons move from the cylinder to the cube
4. Protons move from the cylinder to the cube
5. There is no net movement of electrons

6. A metal cube with a positive charge +Q₁ is brought into contact with a cylinder of a positive charge +Q₂ where |Q₁|<|Q₂|.

A correct choice describing the net movement of charges is … .

1. Electrons move from the cube to the cylinder.
2. Protons move from the cube to the cylinder.
3. Electrons move from the cylinder to the cube.
4. Protons move from the cylinder to the cube.
5. There is no net movement of electrons.

7. When two electric charges are held at a distance of r, the electrostatic force between them is F_E. The distance between the charges is then doubled. The new electrostatic force between the charges is … 

1. 4 F_E
2. (¼) F_E
3. (½) F_E
4. 2 F_E
5. 5 F_E

8. When two electric charges, q₁ and q₂, are held a distance r apart, the electrostatic force between them is F_E. The charge of q₁ is then doubled. The new electrostatic force between the charges is …

1. 4 F_E
2. (¼) F_E
3. (½) F_E
4. 2 F_E
5. 5 F_E

9. The picture below shows two point clusters of charge situated in free space and placed on a line that is called the x-axis. The first, with a positive charge of Q₁ = +8e, is at the origin. The second, with a negative charge of Q₂ = -4e, is to the right at a distance equal to 0.2 m. The magnitude of the force between them is … . 
   (e=1.6 × 10^-19 C)

1. 1.84 × 10^-25 N
2. 1.80 × 10^-24 N
3. 3.20 × 10^-24 N
4. 1.60 × 10^-23 N
5. 1.81 × 10^-22 N

10. The charge +q is placed 2 m from the charge -q, the electric force on the charge -q is F. Another charge +q is placed right in the middle of the two charges. The electric force on the charge –q is … .

1. 5 F
2. 2 F
3. 1.5 F
4. 1.25 F
5. 0.5 F

11. Three equal charges +q are each placed at the corners of a square with side length r as shown in the figure. The force magnitude on the charge B is … .

A.    B.    C.    D.    E.

12. In the vicinity of point charge q, we place a 0.208 μC-charge so that a force of 5.00 x 10^-5 N applied on it due to the charge q. The electric field produced by this unknown charge q is … .
    (k = 8.99 x 10⁹ Nm²/C²)

1. 220 N/C
2. 240 N/C
3. 260 N/C
4. 280 N/C
5. 300 N/C

13. The electric field due to a point charge of 41.6 μC at a distance of 1 meter away from the charge is … .

(k = 8.99 x 10⁹ Nm²/C²)

1. 1.75 × 10⁵ N/C
2. 1.87 × 10⁵ N/C
3. 3.74 × 10⁵ N/C
4. 4.65 × 10⁵ N/C
5. 8.75 × 10⁵ N/C

14. The electric field strength at a distance r from the charge q will be enlarged to 125 times the original. This can be done by … .

1. increasing the charge to 5 times and the distance to 25 times
2. reducing the distance to 1/5 times and increasing the charge by 25 times
3. reducing the distance to 1/125 times and increasing the charge 5 times
4. increasing the distance to 125 times
5. increasing the charge to 5 times and reducing the distance to 1/5 times

15. Two charges (q₁ and q₂) are separated by a distance d. Between the two charges and their connection, there is a point P and a distance of 2/3 from q₁. If the field strength at point P is zero, then … .

1. q₁ and q₂ are dissimilar charges
2. the electric potential at point P caused by q₁ and q₂ is equal
3. the electric potential at point P is zero
4. the charge q₁ = 2 times the charge q₂
5. the charge q₁ = 4 times the charge q₂

16. The electric potential at a distance r from the charge Q is 794 V. The intensity of the field at that point is 438 N/C. If k= 8.99 x 10⁹ Nm²/C², then the charge Q is … .

1. 2.25 x 10^-9 C
2. 4.8 x 10^-8 C
3. 3.2 x 10^-8 C
4. 1.6 x 10^-7 C
5. 1.6 x 10^-9 C