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

A measure of how much a material opposes the flow of electric current. It's a property of the material itself.

The ratio of voltage across a conductor to the current flowing through it. It's measured in ohms (Ω).

An electrical device that converts electrical energy into other forms of energy, often heat. All conductors have some resistance, so they can be considered resistors.

A resistor whose resistance value can be adjusted.

The conversion of electrical potential energy into thermal energy due to the flow of electricity through a material. This energy loss is directly related to the resistance of the material.

The amount of electrical energy converted into heat or other forms of energy per unit of time. It is measured in watts (W).

The rate at which electrical energy is transmitted at voltages typically greater than 100 kV (kilovolts).

The property of a material that opposes the flow of electric current. It is measured in ohms (Ω).

The relationship between voltage, current, and resistance. It states that the current flowing through a conductor is directly proportional to the voltage applied across its ends and inversely proportional to its resistance. Mathematically, it is expressed as V = IR.

The relationship between electrical energy, current, resistance, and time. It states that the heat produced in a conductor is proportional to the square of the current, the resistance, and the time for which the current flows. Mathematically, it is expressed as W = I²Rt.

The process of transmitting electrical energy over long distances at high voltages. This reduces energy loss as heat, improving efficiency.

In a series circuit, the current is the same at every point throughout the circuit.

In a parallel circuit, the current splits at junctions and recombines later. The total current before the split and after the join is the same.

The sum of currents entering a point in a circuit equals the sum of currents leaving that point.

The total potential difference (voltage) across the circuit equals the sum of the potential differences across each component.

The total resistance in a series circuit is the sum of the resistances of each individual component.

The reciprocal of the total resistance in a parallel circuit is the sum of the reciprocals of each individual resistance.

A variable resistor (like a rheostat) can be adjusted to change the resistance value in a circuit.

A potentiometer is a specific type of variable resistor with a sliding contact that allows for adjusting the output voltage. It can be used as a potential divider.

The ability of a material to oppose the flow of electric current. It is measured in ohms (Ω).

A measure of how much a material resists the flow of electric current when a particular size and shape of that material is considered. Measured in ohm-meters (Ωm).

A device used to measure an unknown electrical resistance by comparing it with a known resistance. It works on the principle of a balanced Wheatstone bridge.

The change in resistance of a material due to temperature. In most conductors, resistance increases with temperature.

A device that uses a micrometer screw for precise measurements of small distances like the diameter of a wire.

The arrangement of two or more resistors in a circuit where the same current flows through each resistor.

The arrangement of two or more resistors in a circuit where the voltage across each resistor is the same.

The combined resistance of multiple resistors connected in a circuit.

The relationship between resistance (R) and cross-sectional area (A) is inversely proportional. A larger cross-sectional area means lower resistance.

In a metallic conductor, resistance increases with temperature. This is because increased thermal energy makes atoms vibrate more, hindering electron flow.

A device that allows for the adjustment of resistance. It can be used to regulate current flow.

The process where a metal, heated to a high temperature, releases electrons from its surface. Happens because thermal energy overcomes the forces holding electrons within the metal.

A partially ionized gas containing ions and free electrons. Unique properties include electrical conductivity, responsiveness to magnetic fields, and high-energy particle interactions.

The carriers of electric current in metals are electrons.

The carriers of electric current in gases are ions (both positive and negative).

The carriers of electric current in electrolytes are ions (both positive and negative).

A circuit designed to measure the resistance of an unknown resistor. It uses a balanced bridge with known resistances to determine the unknown value.

A simplified version of the Wheatstone bridge where a single wire of known length acts as two resistors. Used for measuring unknown resistances.

A thermistor or LDR used as part of a Wheatstone bridge to measure changes in temperature or light intensity respectively.

The relationship between current and voltage for a metallic conductor at constant temperature. Follows Ohm's law.

The relationship between current and voltage for an ionic solution with inactive electrodes. Shows a gradual increase in current with increasing voltage, but with a limiting value.

The formula P = VI is used to calculate electrical power. It connects voltage (V), current (I) and power (P).

High voltages are used to reduce energy loss as heat during long distance transmission.

The energy loss (as heat) in a transmission line is proportional to the square of the current (W=I^2R).

Using copper for transmission lines reduces resistance and improves efficiency due to its excellent conductivity and low resistivity.