Drift velocity derivation

In this post, you will find solved Numericals on drift velocity for class 12. These numerical problems are based on the drift velocity of electrons and electric current. ( see the derivation of electric current and drift velocity equation ) Formulas Used Electric Current I = nAve Mean drift velocity v = I /[nAe] where A = area of cross-section of the conductor, n = number of electrons per cubic meter, e = charge on each electron, and v = drift velocity of the electron. Numericals on Drift Velocity for Class 12 [solved] 1 ] A copper wire has a cross sectional area of 7.85 x 10 -7 m 2. The number density of copper is 8.5 x 10 28 m -3. Calculate the mean drift velocity of the electrons through the wire when the current is 1.4 A. Solution: The equation to use: I = nAve ( see the derivation of the drift velocity equation ) => mean drift velocity = v = I/(nAe)…. ……… (1) As per the problem statement, A=7.85 x 10 -7 m 2 n=8.5 x 10 28 m -3 and I = 1.4 A We know, e=1.6 x 10 -19 Putting all the values in equation 1, we will get: v= 1.31 x 10 -4 m/s Drift velocity Numerical Extra Questions as exercise Now solve the following numerical problems using the same formula. Take Away | Suggested reading Here we have solved numerical problems on the drift velocity of electrons and electric current. You can go through the following related and suggested posts for a better understanding of the topic. drift velocity and current – how slow drift velocity causes high-speed current derive the relat...

In this post, we will derive the drift velocity formula and understand the concepts of the drift velocity of an electron. Drift velocity formula The drift velocity formula in terms of Relaxation Time is as follows: v d = a τ [we will derive this here] The drift velocity formula in terms of Electric Field is as follows: v d = ( Ee/m) τ [we will derive this here] The drift velocity formula in terms of electric current: v d = I/[neA]. We have a separate post on this here: v d = a τ The free electrons in metals move at random due to thermal agitation. During this motion, the free electrons collide with stationary positive ions and the direction of motion of the free electrons changes after each collision. Hence, the average thermal velocity of all the free electrons is zero. It means that there is no net motion of the free electrons in any particular direction. When a battery is connected across the metal wire, a Potential Difference (PD) is established between the ends of the wire, and an electric field is produced at every point of the wire. Each free electron experiences an electric force. Due to this electric force, the electrons get accelerated in the direction opposite to the direction of the electric field. The acceleration of the electron of mass m can be expressed as a = F/m = eE/m. a = F/m = E e/m …………. (1) Let’s consider an electron under the effect of the applied electric field E. See also Joule's Law of Heating | Joule's Law of heating class 10 Let’s τ 1 be its re...

Contents • 1 Gyration • 2 Parallel motion • 3 General force drifts • 3.1 Gravitational field • 3.2 Electric field • 3.3 Nonuniform E • 4 Nonuniform B • 4.1 Grad-B drift • 4.2 Curvature drift • 4.3 Inertial drift • 4.4 Curved vacuum drift • 5 Polarization drift • 6 Diamagnetic drift • 7 Drift Currents • 8 References • 8.1 External links Gyration If the magnetic field is uniform, the particle velocity is perpendicular to the field, and other forces and fields are absent, then the magnetic gyration around the magnetic field. For mass m, charge q, and magnetic field B, the frequency of the circular motion, the gyro-frequency or cyclotron frequency, is \(\omega_\) Drift Currents With the important exception of the E-cross-B drift, the drift velocities of different species will be different. The differential velocity of charged particles results in a current, while the mass dependence of the drift velocity can result in chemical separation. References Cosmic Plasma (1981), Hannes Alfvén External links • Subsections and from • • “The Exploration of the Earth’s Magnetosphere” by David P. Stern and Mauricio Peredo Categories

What is Drift Current? Derivation: The flow of charge carriers in response to the Drift Current Once an electric field is applied to a semiconductor, charge carriers will begin to flow for generating current. The holes in the semiconductor will flow through the electric field whereas the electrons will flow opposite to the electric field. Here, each charge carrier flow can be described as a constant drift velocity (Vd). The sum of this current mainly depends on the attention of charge carriers & their mobility within the material. Please refer to this link to know about Drift Current in Semiconductor We know that there are two types of charge carriers present in semiconductor namely electrons & holes. Once the electric field is applied to a semiconductor, then the flow of electrons will be in the direction of +Ve terminal of a battery whereas holes will flow in the direction of –Ve terminal of a battery. Drift Current in Semiconductor In a semiconductor, the negative charge carriers are electrons and positively charged carriers are holes. We have already discussed that the direction of electrons flow will be attracted by the positive terminal of the battery whereas the holes are attracted by the negative terminal of the battery. In a semiconductor material, the flow of electrons direction will be changed because of the continuous collision through the atoms. Every time the electron flow will strike an atom & bounces back within a random way. The voltage applied to a semico...

In this post, we will see how the drift velocity of an electron is related to its mobility. The drift velocity of an electron can be expressed as v d = ( Ee/m) τ, where v d is the drift velocity, E is the electric field, e is the charge of an electron, and m is the mass of an electron. You can find the The drift velocity of an electron v d = ( Ee/m) τ …………….. (1) (v d is the drift velocity, E is the electric field, e is the charge of an electron, and m is the mass of an electron.) This equation can be rewritten as the following: => v d = ( τe/m) E …………. (2) τe/m is a constant and it is known as the mobility of electron (μ e). So, we can write the equation of the drift velocity using mobility: v d = μ e E ……………. (3) equation of the drift velocity using mobility Now, when electric field E is 1 V m -1, then equation (3) gives this equation of drift velocity in terms of mobility of an electron only: v d = μ e when E = 1 V m -1 So, we can define mobility in this way: Mobility of an electron is the drift velocity of an electron under the effect of an electric field equalling 1 V/m. Related Posts: • How Small drift speed of electron causes high-speed electric current? • Drift velocity formula • Drift velocity Derivation • Numericals on Drift Velocity class 12 • Derive the relation between Current and Drift Velocity • Derivation of Ohm's Law class 12 (using drift velocity equations)

I have a question on the derivation of the average drift velocity in a conductor: drift velocity is the average velocity which a free charge moving in a conductor has due to the influence of an electric field applied to the conductor. In a metal, the free charge will be an electron. As they move through the conductor, electrons will frequently bump into ions. If τ is the mean free time of the electron, i.e. the average time between successive collisions, then between two collisions, the action of an external electric field will make the electron accelerate by (E*e/m)*τ, where E is the strength of the field (and this strength is constant), e the charge of an electron, an m the mass of the electron. In common textbooks this quantity (E*e/m)*τ is equal to the magnitude of the drift velocity in the conductor. This confuses, since the quantity expresses the average maximum speed gained by the electron, i.e. the speed it has just before it collides with the next ion. But drift velocity is supposed to be the average velocity of the electron due to the field, so I think its magnitude should be just one-half of this quantity. I think the textbook description is a case of getting out of hand. If you check To be fair to the textbook presentation, such a description usually comes up in a discussion of why many materials are Ohmic, specifically the situation of low-field mobility, which is often constant (drift velocity being proportional the applied electric field). The idea being tha...