It should be noted that AC (Alternating and DC (Direct Current ) are two types of the same form of energy i.e electric

current.

The only major difference between these two is the polarity, DC

has fixed polarity (poles remain as they are, all throughout) and AC has shifting poles whose polarity changes alternatively

in a continuous manner.

Because of this vibrative nature of AC, it constitutes of an additional

element called frequency which gives indicates the magnitude of

the discussed vibration.

This is why same voltage reading is expressed differently in both, for e.g. DC: 220 V and AC: 220 V, 50 Hz

Voltage drops

Whenever current passes through a resistance of some kind, a voltage drop occurs across that resistance. The amount of the drop is given by Ohm's Law: 

V=IR 

Where: 

V = The value of the voltage drop 

I ₌ The current through the circuit in amperes

R = The total resistance of the circuit 

Let's say you have a simple series circuit containing a 10-volt battery, a 3-ohm resistor, and a 2-ohm resistor in series with each other (if the resisitors are in parallel the voltage drop across the "system" of resistors is equivalent to the input voltage of the system, in this example 10 volts. The current flow through each resistor can then be calculated using Ohm's Law). Ohm's Law tells us that 2 Amps are flowing in the circuit (I = V/R = 10/5 = 2). The voltage drop across the 3-ohm resistor is 6 volts (V = IR = 2*3 = 6).

The orderd flow of electric charges through a conductor is called electric current and it equal to charge flowing per unit time, i.e., current = charge/time. Its SISI unit is an ampere (A).

Self Inductance of a coil is the magnetic flux linked with the coil when the current through coil is IA

ϕ=li where L is the constant of proportionality .

Let a source of emf be connected to an inductor L 

With increase in current ,the opposite emf ,e=−Ldtdi​

Work done dw=∣e∣idt=Lidtdi​dt=Lidi

W=∫0i​Lidi=21​Li2

Energy stored in magnetic inductor,U=21​Li2

A. 

- A pair of equal and opposite charges seperated by a small vector distance is called an electric dipole. - An ideal dipole consists of two very very large charges + q and -q seperated by a very very small distance.

- An ideal dipole has almost no size.

- Molecules are made up of positive and negative charges seperated by small distances like water, ammonia etc and they act as electric dipoles. - Molecules which have non uniform distribution of charge are known as polar.Polar molecules will always be slightly negative on one end and slightly positive on the other Polar molecules are said to be permanent dipoles.

Eg: water, carbon dioxide.

As per the Gauss theorem, the total charge enclosed in a closed surface is proportional to the total flux enclosed by the surface. Therefore, If ϕ is total flux and ϵ0 is electric constant, the total electric charge Q enclosed by the surface is; Q = ϕ ϵ0.

Aim
To compare the EMF of two given primary cells using potentiometer.

Apparatus
Potentiometer, a Leclanche cell, a Daniel cell, an ammeter, a voltmeter, a galvanometer, a battery (or battery eliminator), a rheostat of low resistance, a resistance box, a one way key, a two way key, a jockey, a set square, connecting wires and a piece of sand paper.

Theory

where, E₁ and E₂ are the e.m.f. of two given cells and l₁ and l₂  are the corresponding balancing lengths on potentiometer wire.

Circuit diagram

Procedure

1. Arrange the apparatus as shown in circuit diagram figure.
2. Remove the insulation from the ends of the connecting copper wires with a sand paper.
3. Measure the e.m.f. (E) of the battery and the e.m.fs. (E₁ and E₂ ) of the cells. See that E > E₁  and also E > E₂ .
4. Connect the positive pole of the battery (a battery of constant e.m.f.) to the zero end (P) of the potentiometer and the negative pole through a one-way key, an ammeter and a low resistance rheostat to the other end (Q) of the potentiometer.
5. Connect the positive poles of the cells E₁ and E₂  to the terminal at the zero end (P) and the negative poles to the terminals a and b of the two way key.
6. Connect the common terminal c of the two-way key through a galvanometer (G) and a resistance box (R.B.) to the jockey J.
7. Take maximum current from the battery making rheostat resistance zero.
8. Insert the plug in the one-way key (K) in circuit and also in between the terminals a and c of the two-way key.
9. Take out a 2,000 ohms plug from the resistance box (R.B.).
10. Press the jockey at the zero end and note the direction of deflection in the galvanometer.
11. Press the jockey at the other end of the potentiometer wire. If the direction of deflection is opposite to that in the first case, the connections are correct. (If the deflection is in the same direction then either connections are wrong or e.m.f. of the auxiliary battery is less).
12.  Slide the jockey gently over the potentiometer wires till you obtain a point where galvanometer shows no deflection.
13. Put the 2000 ohms plug back in the resistance box and obtain the null point position accurately, using a set square.
14. Note the length l₁ of the wire for the cell E₁ Also note the current as indicated by the ammeter.
15. Disconnect the cell E₁  by removing the plug from gap ac of two-way key and connect the cell E₂  by inserting plug into gap be of two-way key.
16. Take out a 2000 ohms plug from resistance box R.B. and slide the jockey along potentiometer wire so as to obtain no deflection position.
17. Put the 2000 ohms plug back in the resistance box and obtain accurate position of null point for second cell E₂ .
18. Note the length l₂  of wire in this position for the cell E₂ . However, make sure that ammeter reading is same as in step 14.
19. Repeat the observations alternately for each cell again for the same value of current.
20. Increase the current by adjusting the rheostat and obtain at least three sets of observations in a similar way.
21. Record your observations as given below

Observations

Calculations

1. For each observation find mean l₁ and mean l₂  and record in column 3c and 4c.
2. Find E₁/E₂ for each set, by dividing mean l₁  (column 3c) by mean l₂  (column 4c).
3. Find mean E₁/E₂ .  

Result

Precautions

1. The connections should be neat, clean and tight.
2. The plugs should be introduced in the keys only when the observations are to be taken.
3. The positive poles of the battery E and cells E₁ and E₂  should, all be connected to the terminal at the zero of the wires.
4. The jockey key should not be rubbed along the wire. It should touch the wire gently.
5. The ammeter reading should remain constant for a particular set of observation. If necessary, adjust the rheostat for this purpose.
6. The e.m.f. of the battery should be greater than the e.m.f.’s of the either of the two
   cells.
7. Some high resistance plug should always be taken out from resistance box before the jockey is moved along the wire.

Sources of error

1. Same as in previous experiments.
2. The auxiliary battery may not be fully charged.
3. The potentiometer wire may not be of uniform cross-section and material density throughout its length.
4. End resistances may not be zero.

Rainbow

• Rainbow is a phenomenon due to combined effect of dispersion, refraction and reflection of sunlight by spherical water droplets of water.
• Rainbow appears when the sun is shining in on one part of the sky (say near western horizon) while it is raining in the opposite part of the sky (say eastern horizon).
• Sunlight is first refracted as it enters a raindrop, which causes the different wavelengths (colours) of white light to separate.
• Longer wavelength of light (red) are bent the least while the shorter wavelength (violet) are bent the most.
• The rays strike the inner surface of the water drop and get internally reflected if the angle between the refracted ray and normal to the drop surface is greater than the critical angle (48º, in this case).
• The reflected light is refracted again as it comes out of the drop as shown in the figure.

In spite of having same level of doping the conductivity of an n-type semiconductor is greater than p-type semiconductor because the charge carrier of a n-type semiconductor is electron which is faster to move than the hole which is the charge carrier of a p-type semiconductor. In other words electrons are more mobile than the holes which makes conduction in n-type semiconductor faster.

The conductivity of n-type semiconductor is greater than that of the p-type semiconductor because mobility of electrons is greater than that of holes.

When displacement vectors are added, the result is a resultant displacement. But any two vectors can be added as long as they are the same vector quantity. If two or more velocity vectors are added, then the result is a resultant velocity. If two or more force vectors are added, then the result is a resultant force. If an object moves relative to a reference frame—for example, if a professor moves to the right relative to a whiteboard, or a passenger moves toward the rear of an airplane—then the object's position changes. This change in position is known as displacement.

The gold leaf electroscope is an instrument for detecting and measuring static electricity or voltage.

Apparatus:

A metal disc is connected to a narrow metal plate and a thin piece of gold leaf is fixed to the plate. This arrangement is insulated from the body of the instrument with an outer cover. A glass front allows you to watch the behaviour of the leaf.

Working:

The electroscope detects charge in the following way:

• A charged object is brought in contact with the open end of the wire. The charges are transferred via the wire which is a good conductor of electricity.
• The gold leaf plates also get charged and since they are similarly charged, they repel and move away from each other.
• This confirms the presence of charge on the body.

Grounding / Discharging

If the charged body was brought close to the electroscope and then, we simultaneously touch the metal plates with our hand, then this would cause the charges to flow through your body (our body is a good conductor of electricity) to the ground. This is called grounding.

A galvanometer is a device that is used to detect small electric current or measure its magnitude. The current and its intensity is usually indicated by a magnetic needle’s movement or that of a coil in a magnetic field that is an important part of a galvanometer.