Electric Current and Resistance Quiz
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Questions and Answers

What is the SI unit of electric current?

  • Coulomb (C)
  • Volt (V)
  • Ohm (Ω)
  • Ampere (A) (correct)

    • What is the relationship between the instantaneous current and the net charge flowing across a section of a conductor in a small time interval?

  • Instantaneous current is the ratio of the net charge to the time interval, as the time interval approaches zero. (correct)
  • Instantaneous current is the square root of the product of the net charge and time interval.
  • Instantaneous current is the product of the net charge and time interval.
  • Instantaneous current is the difference between the net charge and the time interval.

    • What does the direction of conventional current in an electric circuit represent?

  • The direction of the magnetic field produced by the current.
  • The direction of the electric field in the circuit.
  • The direction of flow of negative charges in the circuit.
  • The direction of flow of positive charges in the circuit. (correct)

    • Which of the following statements is true about electric current?

    <p>Electric current is a scalar quantity and has only magnitude. (C)</p> Signup and view all the answers

    A steady current of 10 mA flows through a conductor. How many electrons pass a given point in the conductor in 1 minute?

    <p>$6.25 imes 10^{16}$ electrons (D)</p> Signup and view all the answers

    A conductor has a length of 10 cm and a cross-sectional area of 2 cm². If its resistance is 5 ohms, what is the resistivity of the material?

    <p>10 Ωm (B)</p> Signup and view all the answers

    Two wires, A and B, are made of the same material. Wire A has twice the length and half the cross-sectional area of wire B. What is the ratio of the resistance of wire A to wire B?

    <p>4:1 (C)</p> Signup and view all the answers

    A conductor has a resistance of 10 ohms. What is the potential difference across the conductor if the current through it is 2 amperes?

    <p>20 volts (D)</p> Signup and view all the answers

    Which of the following factors does NOT affect the resistivity of a conductor?

    <p>Length of the conductor (A)</p> Signup and view all the answers

    A current of 5 amperes flows through a conductor of cross-sectional area 10 cm². What is the current density in the conductor?

    <p>500 Am⁻² (A)</p> Signup and view all the answers

    What is the relationship between current and charge flow through a conductor?

    <p>Current is the amount of charge flowing per unit time. (D)</p> Signup and view all the answers

    Which statement accurately describes the direction of conventional current flow?

    <p>The direction of conventional current is opposite to the direction of electron flow. (A)</p> Signup and view all the answers

    Which of these scenarios results in zero net electric current within a solid conductor?

    <p>When there is no electric field present within the conductor. (B)</p> Signup and view all the answers

    What are the current carriers responsible for electrical conductivity in electrolytic solutions?

    <p>Ions (C)</p> Signup and view all the answers

    According to Ohm's law, what is the relationship between potential difference (V), current (I), and resistance (R) in a conductor?

    <p>V = I * R (C)</p> Signup and view all the answers

    If the free electron density of a conductor is doubled, what happens to the conductivity of the conductor?

    <p>It is doubled. (C)</p> Signup and view all the answers

    Which of the following is NOT a characteristic of an ideal conductor?

    <p>High thermal conductivity (C)</p> Signup and view all the answers

    What is the primary factor responsible for the existence of free charged particles in the upper atmosphere?

    <p>Cosmic rays (D)</p> Signup and view all the answers

    What is the relationship between the relaxation time of electrons and the conductivity of a metal?

    <p>The conductivity is directly proportional to the relaxation time. (C)</p> Signup and view all the answers

    In the equation $j = \sigma E$, what does the term $j$ represent?

    <p>Current density (C)</p> Signup and view all the answers

    Which of the following accurately describes the drift of electrons?

    <p>Electrons moving randomly in the opposite direction to the electric field. (C)</p> Signup and view all the answers

    What is the relationship between the conductivity of a conductor and its resistivity?

    <p>Conductivity and resistivity are inversely proportional. (D)</p> Signup and view all the answers

    What does Ohm's law state in terms of current density and conductivity?

    <p>Current density is equal to the product of conductivity and electric field. (C)</p> Signup and view all the answers

    If the relaxation time of electrons in a metal doubles, what happens to the conductivity of the metal?

    <p>The conductivity doubles. (D)</p> Signup and view all the answers

    What is the approximate average velocity of free electrons in a metal at room temperature?

    <p>10^-3 m/s (B)</p> Signup and view all the answers

    How is the drift velocity of electrons in a conductor related to the electric field strength?

    <p>Drift velocity is directly proportional to the electric field strength. (D)</p> Signup and view all the answers

    Which of the following is TRUE about the relationship between the resistance of a conductor and its dimensions?

    <p>Resistance is directly proportional to the length of the conductor and inversely proportional to its cross-sectional area. (A)</p> Signup and view all the answers

    What is the key difference between resistance and resistivity?

    <p>Resistance is a property of a specific conductor, while resistivity is a property of the material the conductor is made from. (A)</p> Signup and view all the answers

    Imagine you have a conductor with constant cross-sectional area. If you double the length of the conductor, what happens to its resistance?

    <p>The resistance doubles. (C)</p> Signup and view all the answers

    Which of the following is a reason why the resistance of a conductor might increase with temperature?

    <p>The relaxation time of free electrons decreases with increasing temperature. (A)</p> Signup and view all the answers

    A circuit contains two resistors connected in series: a 10 Ω resistor and a 20 Ω resistor. What is the equivalent resistance of this series combination?

    <p>30 Ω (A)</p> Signup and view all the answers

    What is the primary factor responsible for the change in a conductor's resistance with temperature?

    <p>The relaxation time of free electrons (A)</p> Signup and view all the answers

    A resistor and a conductor made of the same material are connected in series. Which has the higher resistivity?

    <p>Both have the same resistivity (C)</p> Signup and view all the answers

    A conductor has a resistance of 10 ohms. If its length doubles and its cross-sectional area is halved, what is the new resistance?

    <p>40 ohms (A)</p> Signup and view all the answers

    Which of the following scenarios could be applied to a wire made of a material with a high resistivity?

    <p>It is used as an efficient heating element in a toaster (B)</p> Signup and view all the answers

    Which of these statements correctly describes the relationship between current and drift velocity?

    <p>Current is directly proportional to the drift velocity (C)</p> Signup and view all the answers

    A copper wire and a nichrome wire of the same dimensions are connected in series to a battery. Which wire will have a higher temperature rise?

    <p>The nichrome wire (D)</p> Signup and view all the answers

    A semiconductor material is unique because its resistivity...

    <p>can either increase or decrease with increasing temperature (B)</p> Signup and view all the answers

    Imagine two identical wires made of the same material but one is twice as long as the other. How do their resistances compare?

    <p>The longer wire has twice the resistance of the shorter wire (D)</p> Signup and view all the answers

    Which devices are classified as non-ohmic?

    <p>Transistor (D)</p> Signup and view all the answers

    What happens to the resistivity of semiconductors when temperature increases?

    <p>Resistivity decreases due to increased electron mobility (A)</p> Signup and view all the answers

    Which of the following arrangements correctly reflects the resistivity order of materials?

    <p>Conductors &lt; Semiconductors &lt; Insulators (A)</p> Signup and view all the answers

    Which statement about the applicability of Ohm's law is true?

    <p>Ohm's law does not hold at very high and very low temperatures. (A)</p> Signup and view all the answers

    What is the primary characteristic of ohmic devices?

    <p>They adhere to Ohm's law consistently. (A)</p> Signup and view all the answers

    If the electric field inside a conductor is doubled, what happens to the drift velocity of electrons?

    <p>It is doubled. (A)</p> Signup and view all the answers

    At a higher temperature, the relaxation time of electrons in a metallic conductor typically:

    <p>Decreases. (A)</p> Signup and view all the answers

    What is the relationship between the electron mobility ($\mu$) and the relaxation time ($\tau$)?

    <p>$\mu$ is directly proportional to $\tau$. (A)</p> Signup and view all the answers

    Which of the following statements is true about the mobility of charge carriers?

    <p>It is affected by the temperature and the type of material. (D)</p> Signup and view all the answers

    Which of these pairs of materials has a resistivity that decreases with increasing temperature?

    <p>Germanium and Silicon (C)</p> Signup and view all the answers

    How does the resistivity of nichrome change with temperature?

    <p>It increases linearly with the increase of temperature. (A)</p> Signup and view all the answers

    What is the expression for the variation of resistivity of a conductor with temperature?

    <p>$ρ = ρ_0 [1 + α(T - T_0)]$ (C)</p> Signup and view all the answers

    What is the behavior of the resistivity of a semiconductor as temperature increases?

    <p>It decreases. (A)</p> Signup and view all the answers

    Which of the following characteristics is NOT suitable for a fuse wire?

    <p>Durability under high temperatures. (B)</p> Signup and view all the answers

    What is a key characteristic of heating elements?

    <p>They should have high resistivity. (D)</p> Signup and view all the answers

    What characteristic of manganin and constantan makes them suitable for wire wound standard resistors?

    <p>They possess negligible temperature coefficients of resistivity. (A), They have high resistivity and low resistance change with temperature. (D)</p> Signup and view all the answers

    Which formula correctly describes the relationship between electrical energy and power?

    <p>$E = Pt$ (A), $P = rac{E}{t}$ (C)</p> Signup and view all the answers

    In terms of electrical power, how can it be expressed using current and resistance?

    <p>$P = I^2R$ (A), $P = V^2 / R$ (C)</p> Signup and view all the answers

    What happens to the power dissipated in a resistor as the current increases?

    <p>It increases exponentially with the square of the current. (A)</p> Signup and view all the answers

    Why is electrical power transmitted at high voltage and low current over long distances?

    <p>To reduce heat loss due to resistance in the transmission lines. (B)</p> Signup and view all the answers

    How is heat generated in a resistor related to the electrical energy being converted?

    <p>It is equal to the change in potential energy as charge moves. (D)</p> Signup and view all the answers

    What does the expression for heat developed in a resistor, caused by electric current, imply?

    <p>It results from the work done by potential energy changes. (A)</p> Signup and view all the answers

    Which statement is true regarding electrical energy and electrical power?

    <p>Electrical energy is the work done to move a charge, while power is the energy used per second. (C)</p> Signup and view all the answers

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