Physics: Resistance and Current Relationships

Resistance (R) is defined as the ratio of voltage (V) across an object to the current (I) flowing through it, represented by the formula $R = \frac{V}{I}$.

High resistance indicates that a significant percentage of electrical energy is dissipated as heat while flowing through the conductor.

Resistivity ($\rho$) is calculated using the formula $\rho = \frac{R \cdot A}{l}$, where R is resistance, A is the cross-sectional area, and l is the length.

<p>A larger diameter results in a larger cross-sectional area, which decreases resistance, while a smaller diameter increases resistance.</p> Signup and view all the answers

<p>An ohmmeter is used to measure resistance, functioning by applying a voltage to the material and measuring the current that flows through it.</p> Signup and view all the answers

<p>Removing the component prevents interference from the current flowing in the circuit, ensuring an accurate resistance reading.</p> Signup and view all the answers

<p>Using Ohm’s Law, resistance can be calculated with the formula $R = \frac{V}{I}$, where $V$ is voltage and $I$ is current.</p> Signup and view all the answers

<p>Power is calculated using the formula $P = VI$, where $P$ is power, $V$ is voltage, and $I$ is current.</p> Signup and view all the answers

<p>High voltage reduces the current flowing through the transmission line, which decreases energy loss as heat due to resistance.</p> Signup and view all the answers

<p>Total resistance can be calculated using the formula $R = \frac{\rho L}{A}$, where $\rho$ is resistivity, $L$ is length, and $A$ is cross-sectional area.</p> Signup and view all the answers

<p>The heat produced depends on the current flowing through the conductor, its resistance, and the time the current is applied.</p> Signup and view all the answers

<p>In a series circuit, the total current is the same and flows through each component equally.</p> Signup and view all the answers

<p>The total resistance in a parallel circuit is calculated using the formula: $$\frac{1}{R_T} = \frac{1}{R_1} + \frac{1}{R_2}$$.</p> Signup and view all the answers

<p>The sum of the currents entering a junction equals the sum of the currents leaving it; this is known as Kirchhoff's Current Law.</p> Signup and view all the answers

<p>To find the current through a resistor in parallel, use Ohm's Law: $$I = \frac{V}{R}$$, where V is the potential difference across the resistor.</p> Signup and view all the answers

<p>A potential divider allows for the division of voltage across components, providing variable voltages for various applications.</p> Signup and view all the answers

<p>A potentiometer acts as a variable resistor that adjusts the division of voltage across it, allowing for controlled output voltage.</p> Signup and view all the answers

<p>The total voltage drop across resistors in series is equal to the sum of the individual voltage drops, as given by $$V_T = V_1 + V_2 + ...$$.</p> Signup and view all the answers

<p>The voltage drops across the resistors are in proportion to their resistances, splitting the 12 V accordingly.</p> Signup and view all the answers

<p>The effective resistance $R_T$ is given by the formula $\frac{1}{R_T} = \frac{1}{R_1} + \frac{1}{R_2}$.</p> Signup and view all the answers

<p>As temperature increases, the resistance of a metallic conductor also increases due to greater atomic vibration and more obstacles to electron flow.</p> Signup and view all the answers

<p>Active electrodes participate in chemical reactions during electrolysis, while inactive electrodes do not change chemically and provide a conductive path for electrons.</p> Signup and view all the answers

<p>The current decreases as the voltage increases due to rise in resistance from heating up the filament.</p> Signup and view all the answers

<p>As the concentration of ions in an electrolyte increases, its conductivity improves, making it a better conductor.</p> Signup and view all the answers

<p>Resistance (R) is inversely proportional to the cross-sectional area (A) of the wire: $R \propto \frac{1}{A}$.</p> Signup and view all the answers

<p>A back emf prevents current flow until the applied voltage exceeds it, resulting in a delay in current until the emf is overcome.</p> Signup and view all the answers

<p>The effective resistance $R_T$ of resistors in series is the sum: $R_T = R_1 + R_2$.</p> Signup and view all the answers

<p>Resistance decreases with decreasing pressure in gases, allowing ions to move more freely and conduct electricity better.</p> Signup and view all the answers

<p>Adding a fourth 5 Ω resistor in parallel would reduce the total effective resistance of the circuit.</p> Signup and view all the answers

<p>Using the principle of null deflection or by ensuring that the current is equal in both arms of the bridge.</p> Signup and view all the answers

<p>Using the formula $R = \frac{\rho l}{A}$, where $A = \pi r^2$, the resistance can be found by substituting in the provided values.</p> Signup and view all the answers

<p>The resistance of the wire decreases as the temperature drops below $0^ ext{o}C$.</p> Signup and view all the answers

<p>A micrometer may not provide as accurate a measurement of resistance over a longer range compared to a metre bridge.</p> Signup and view all the answers

<p>The resistance decreases as the diameter of the wire increases.</p> Signup and view all the answers

<p>It emits light as the electrons return to lower energy levels.</p> Signup and view all the answers

<p>They convert a high percentage of input energy into visible light.</p> Signup and view all the answers

<p>It is the process where heated metal emits electrons as they gain sufficient energy to escape from the metal's surface.</p> Signup and view all the answers

<p>The charge carriers are ions, which can be cations (positive) or anions (negative).</p> Signup and view all the answers

<p>Metals use electrons as charge carriers, while gases utilize ions and free electrons.</p> Signup and view all the answers

<p>Using the formula R1R2 = R3R4, where R1, R2, R3 are known resistances.</p> Signup and view all the answers

<p>It provides greater accuracy in measuring resistance.</p> Signup and view all the answers

<p>It increases the number of electrons available for conduction, thus increasing the current.</p> Signup and view all the answers

<p>The current does not increase further since all available electrons are already utilized.</p> Signup and view all the answers

<p>The slope of the graph decreases, indicating increased resistance.</p> Signup and view all the answers

<p>A high resistance indicates that a significant percentage of electrical energy is dissipated as heat.</p> Signup and view all the answers

<p>Increasing the length of the wire in a variable resistor increases its resistance.</p> Signup and view all the answers

<p>Resistivity quantifies opposition to current flow and is determined by the material's resistance, cross-sectional area, and length.</p> Signup and view all the answers

<p>Resistors convert electrical potential energy into thermal energy, which can be useful for controlling current flow.</p> Signup and view all the answers

<p>The formula for resistivity is $ ho = \frac{R \cdot A}{l}$, where $R$ is resistance, $A$ is cross-sectional area, and $l$ is length.</p> Signup and view all the answers

<p>7.5 Ω</p> Signup and view all the answers

<p>2.8 MW</p> Signup and view all the answers

<p>Use the formula $\rho = R \cdot \frac{A}{L}$; where A is the cross-sectional area and L is the length.</p> Signup and view all the answers

<p>Energy loss decreases because higher voltage allows for smaller current.</p> Signup and view all the answers

<p>P can be expressed as $P = \frac{V^2}{R}$ or $P = IV$.</p> Signup and view all the answers