Post Test Physics M.5 (T2)

The total resistance in a circuit depends on the voltage supplied by the power source. The resistance in a circuit is determined by the voltage and the current flowing through it. As the voltage increases, the resistance in the circuit also increases. Therefore, the correct answer is "แรงดันไฟฟ้าจากแหล่งจ่ายไฟ" (the voltage supplied by the power source).

เมื่อค่าความต้านทานภายในวงจรขนานสาขาเพิ่มขึ้น จะทำให้กระแสไฟฟ้าลดลง เนื่องจากความต้านทานสูงขึ้นจะกันการไหลของกระแสไฟฟ้าในวงจร ทำให้กระแสไฟฟ้าลดลงตามไปด้วย

The correct answer is the direction opposite to that of the moving positive charges or the direction opposite to that of the moving negative charges. This means that the direction of the electric current is opposite to the direction of the movement of the positive charges or opposite to the direction of the movement of the negative charges.

The correct answer is "พลังงานไฟฟ้า 1.5 J ที่ถ่านไฟฉายจ่ายให้แก่ประจุไฟฟ้า 1 C ซึ่งเคลื่อนที่ในตัวนำ". This answer is correct because it correctly states that the electrical energy supplied by the flashlight battery is 1.5 joules, which moves a charge of 1 coulomb through the conductor.

The number of free electrons moving through the cross-sectional area of the wire can be calculated using the formula:

Number of electrons = (current * time) / (charge of one electron)

Given that the current is 5 Amps and the velocity of the electrons is 7.5 x 10^-5 m/s, we can calculate the number of electrons per unit volume by dividing the current by the charge of one electron. This gives us 5 / (1.6 x 10^-19) = 3.125 x 10^19 electrons per second.

To find the number of electrons per unit volume, we multiply this value by the cross-sectional area of the wire, which is given as 0.7 cm^2 or 7 x 10^-5 m^2. This gives us (3.125 x 10^19) * (7 x 10^-5) = 2.1875 x 10^15 electrons per second per unit volume.

To convert this to the number of electrons per unit volume per unit time, we multiply by the time, which is 1 second. Therefore, the number of electrons per unit volume is 2.1875 x 10^15 electrons per unit volume.

The answer choice that matches this value is 2.7 x 10^27 electrons per unit volume, so it is the correct answer.

กระแสไฟฟ้าไม่ใช่ปริมาณเวกเตอร์ แต่เป็นปริมาณสกัด หรือการสลักของประจุไฟฟ้าผ่านตัวนั้น ๆ ในหน่วยเวลาที่กำหนด ปริมาณเวกเตอร์เป็นปริมาณที่มีทิศทางและขนาด แต่กระแสไฟฟ้าไม่มีทิศทางและขนาด จึงไม่ใช่ปริมาณเวกเตอร์

The correct answer is "มีค่าเท่ากันทุกจุด". This means that the electric current flowing in a closed circuit is the same at every point. This is a fundamental principle in circuit theory known as Kirchhoff's Current Law, which states that the total current entering a junction in a circuit is equal to the total current leaving the junction. Therefore, in a series circuit, where there is only one path for the current to flow, the current remains constant throughout the circuit.

The total current in a parallel circuit is equal to the sum of the currents flowing through each branch. In this question, it is stated that the current flowing through each branch is the same, so the total current in the parallel circuit will be equal to the current flowing through each branch. Therefore, the correct answer is "กระแสไฟฟ้าที่ไหลในแต่ละสาขารวมกัน" (The total current is equal to the current flowing through each branch).

When there is a potential difference between the two ends of a metal rod, an electric current will flow from the end with higher electric potential to the end with lower electric potential. This is because electric charges naturally flow from areas of higher potential to areas of lower potential. Therefore, the correct answer states that the electric current flows from the end of the rod with higher electric potential to the end with lower electric potential.

The battery can deliver a constant current of 5 amps. To find the duration it can last, we need to divide the total charge it can deliver by the current. Given that the battery can deliver 3.6 x 106 coulombs of charge, dividing it by 5 amps gives us 720,000 seconds. Converting this to hours, we get 200 hours. Therefore, the battery can last for 200 hours.

The explanation for the given correct answer is that the voltage drop across each resistor in a circuit depends on its individual resistance. In a series circuit, the total resistance is the sum of the individual resistances, so the voltage drop across each resistor will be proportional to its resistance. Therefore, the voltage drop across each resistor depends on its individual resistance.

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The given answer "It/e" suggests that the amount of free electrons flowing through the cross-sectional area of the wire in time t is equal to the current I divided by the charge of an electron e. This is based on the equation I = nev, where I is the current, n is the number of free electrons per unit volume, e is the charge of an electron, and v is the drift velocity of the electrons. By rearranging the equation, we can solve for the number of free electrons passing through the cross-sectional area, which is equal to It/e.

The question is asking for the number of free electrons that pass through a cross-sectional area when a constant current of 4 amperes flows for 8 seconds. The number of free electrons can be calculated using the formula:

Number of electrons = (current x time) / charge of electron

Plugging in the values, we get:

Number of electrons = (4 A x 8 s) / (1.6 x 10^-19 C)

Simplifying the equation, we get:

Number of electrons = 32 / (1.6 x 10^-19)

Number of electrons = 2 x 10^19 / (1.6 x 10^-19)

Number of electrons = 2 x 10^19 x 10^19 / 1.6

Number of electrons = 12.5 x 10^38

Expressing in scientific notation, we get:

Number of electrons = 1.25 x 10^39

Therefore, the correct answer is 1.6 x 10^20 particles.

The current passing through the internal resistance of each cell is the same, regardless of how many cells are connected in series. When the cells are connected in parallel, the total current passing through the external resistance is 1.5 times the current passing through each cell. This suggests that the total resistance in the parallel circuit is 1.5 times the internal resistance of each cell. Therefore, the internal resistance must be half of the total resistance in the parallel circuit, which is 2.0R.

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The formula to calculate the current (I) is given by I = Q / t, where Q is the charge and t is the time. In this question, the charge is given as 180 coulombs and the time is given as 2 minutes. We need to convert the time to seconds, so 2 minutes is equal to 2 * 60 = 120 seconds. Plugging these values into the formula, we get I = 180 coulombs / 120 seconds = 1.5 amperes. Therefore, the correct answer is 1.5 A.

The correct answer is 0.28 Amps. When the student initially connected the batteries incorrectly, the total voltage in the circuit was 8V - 6V = 2V. The total resistance in the circuit is 48 ohms. Using Ohm's Law (V = IR), we can calculate the current in the circuit: I = V/R = 2V / 48 ohms = 0.04 Amps. When the batteries are correctly connected, the total voltage is 8V + 6V = 14V. Using the same formula, we can calculate the current in the circuit: I = V/R = 14V / 48 ohms = 0.28 Amps.

The total resistance in a series circuit is equal to the sum of the individual resistances. In this question, we are given three resistors with resistances of 2, 4, and 8 ohms. To find the total resistance, we need to add these resistances together. 2 + 4 + 8 = 14 ohms. Therefore, the correct answer is 1.14 ohms.