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| high school exams |
“Ahl Masr” presents the strongest final review for the exam night in physics for all high school students in the Scientific Division, with physics teacher Tarek Yahya, where he reviews the most important points in physics that are expected to be present in tomorrow’s exam, which is scheduled to start at ten o’clock in the morning Until one o'clock in the afternoon.
Review of the night of the exam in physics
The most important points in physics were as follows:
1- When a part of the coil is cut and the rest is connected to the same source “battery”, the current will increase because the resistance has decreased, and in the case of the same current the current does not change.
2- The break-even point of the wires is always in the subtraction region so that the two fields are opposite to each other and are closer to the wire with the lowest current.
3- In an ohmmeter, if an external resistance is connected, Rx = the resistance of the device, R, the pointer deviates in half, and the external resistance is double the device.
It will deviate to a third and if it is 3 times it is to a quarter and so on.
4- As for the ammeter, the value of the resistance that is connected parallel to the galvanometer to reduce the sensitivity by half and be Rs = Rg, and if the sensitivity is reduced by a third, it will be Rs = Rg ÷ 2
In the case of a quarter
Rg ÷ 3 = Rs
And confirmation by the law of sensitivity or fragmentation which is
Ig ÷ I = Rs ÷ Rs + Rg.
5- As for the voltmeter, if it reaches Rm = Rg..
Sensitivity is halved
If Rm is double, sensitivity will be reduced by a third
6- When light falls on a metal and the electrons are released, their number will increase, and if we increase the intensity of the incident light, it means from faint to bright, or we bring the light source closer.
7- The kinetic energy of the liberated electrons increases by increasing the energy or frequency of the incident light, or by decreasing its wavelength, meaning “we changed the color from red, for example, to yellow, orange, green, and so on.”
8- Inductive reactance works to resist alternating current through the rate of change in the intensity of the current.
9- Capacitive reactance works to resist alternating current by the rate of change in voltage.
10- The value of the magnetic dipole moment does not depend on the position of the coil, but rather on I, A, N only, which is a vector quantity and its direction is always perpendicular to the coil, and its direction can be determined by the rule of the right auger, which is determined by its direction is the direction of the current.
11- The intensity of the electric current in the photovoltaic cell is zero, in two cases: either by falling light whose frequency is less than the critical frequency of the cathode surface, or if we connect the anode to a negative electrode, that is, we reverse the poles.
12- The inductive reactance of the winding is zero, either by connecting it to a DC source or to a double winding.
13- The intensity of the radiation emitted by a radioactive object approaches zero at very short wavelengths "none" and very large "almost non-existent" as is evident in the Planck curve for radiation.
14- The decay of the electric charge in the vibrating circuit can be treated by feeding it every period with additional charges from the battery.
15- The electrical resistance does not stop and is inversely proportional to the intensity of the current.
But the strength of the current is inversely proportional to the electrical resistance.
16- Balance in galvano is equal to the torque of the coil pairing with the torque in the springs, and then its indicator stops at a certain reading.
17- The equilibrium in the thermal ammeter is the amount of thermal energy generated in it equal to the amount of energy lost from it, at which point its expansion stops and the indicator stabilizes at a certain reading.
18- If you find an AC source circuit, a capacitor, and a coil only, here the source voltage is the difference between the coil voltage and the capacitor voltage “VL-Vc”, the angle between them is 180
19- In matters of the transformer.
Any data related to the device to which a radio is connected, for example, or a fan, would be s, meaning “if the fan voltage was said to be ten volts, it would be Vs, and so on, because any device we always connect to with the secondary transformer coil, and the source is the primary.
20- The transformer does not operate on DC; Because the constant current generates a fixed magnetic field, it does not affect the secondary coil except for the opening and closing moments of the primary coil switch.
21- Question units of measurement often in Faraday's law and the laws of self and mutual induction and the transmittance coefficient.
22- The surface potential barrier is an attractive force that prevents an electron from being released from the surface of the metal.
23- The work function is the lowest energy sufficient to liberate an electron from the metal surface without imparting kinetic energy to it.
24- You can listen to a particular radio station when the frequency of the resonant circuit inside the radio is equal to the frequency of the station you want to hear, z = R and impedance = resistance even if you change the station.
25- The motor “motor” never starts its rotation except from a position parallel to the field until a current passes in its coil and it is moved.
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