Current Electricity & Capacitors Flashcards for NEET — 20 cards

First 8 of 20 Current Electricity & Capacitors flashcards

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1. Card 1 of 20

   What is Drift Velocity ($v_d$) and how is it related to Electric Current ($I$)?

   Hint: n = number density of electrons, e = charge of an electron, A = cross-sectional area.

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   Answer

   Drift velocity is the average velocity with which free electrons get drifted towards the positive end of a conductor under the influence of an external electric field. Relation: $I = neA v_d$

2. Card 2 of 20

   Define Electron Mobility ($\mu$) and write its formula.

   Hint: Mobility is always positive. SI unit is $m^2 V^{-1} s^{-1}$.

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   Answer

   Mobility is defined as the magnitude of drift velocity per unit electric field. $\mu = \frac{v_d}{E} = \frac{e\tau}{m}$

3. Card 3 of 20

   State Ohm's Law in Vector Form (Microscopic form).

   Hint: Current density ($J = I/A$) is a vector quantity, unlike electric current.

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   Answer

   $\vec{J} = \sigma \vec{E}$ Where $\vec{J}$ is current density, $\sigma$ is electrical conductivity, and $\vec{E}$ is electric field.

4. Card 4 of 20

   Draw the V-I characteristics for Ohmic and Non-Ohmic conductors.

   Hint: The slope of a V-I graph gives Resistance ($R$).

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   Answer

   Ohmic = Linear. Non-Ohmic = Non-linear.

5. Card 5 of 20

   How does Electrical Resistance ($R$) vary with Temperature ($T$) for metallic conductors?

   Hint: For semiconductors and insulators, $\alpha$ is negative (resistance decreases as temperature increases).

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   Answer

   $R_T = R_0 [1 + \alpha (T - T_0)]$ Where $\alpha$ is the temperature coefficient of resistance. For metals, $\alpha$ is positive, so resistance INCREASES with temperature.

6. Card 6 of 20

   What is the formula for the Terminal Potential Difference ($V$) of a cell discharging current ($I$)?

   Hint: If the cell is being CHARGED, current flows into the positive terminal, and $V = E + Ir$.

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   Answer

   $V = E - Ir$ (Discharging)

7. Card 7 of 20

   What is the equivalent EMF ($E_{eq}$) and internal resistance ($r_{eq}$) when two different cells are connected in PARALLEL?

   Hint: This is a very high-yield formula for NEET. Make sure the polarities match. If they oppose, use a minus sign for the opposing EMF.

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   Answer

   $E_{eq} = \frac{E_1 r_2 + E_2 r_1}{r_1 + r_2}$ $r_{eq} = \frac{r_1 r_2}{r_1 + r_2}$

8. Card 8 of 20

   State Kirchhoff's First Law (Junction Rule) and its underlying conservation principle.

   Hint: Nodes do not accumulate or store charge.

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   Answer

   The algebraic sum of currents meeting at a junction is zero ($\sum I = 0$). Currents entering = Currents leaving. It is based on the Conservation of Charge.