Physics Chapter on Electric Circuits and Optics
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Questions and Answers

What is the formula used to calculate resistance?

  • R = I / V
  • R = I + V
  • R = V + I
  • R = V / I (correct)

If the voltage is 12 V and the current is 1.5 A, what is the resistance?

  • 10 Ω
  • 6 Ω
  • 8 Ω (correct)
  • 12 Ω

What is the function of the thermocouple in the context of detecting light from the Sun?

  • To measure the intensity of visible light
  • To convert light into electrical energy
  • To reflect sunlight towards a prism
  • To detect infra-red rays (correct)

What is the role of a variable resistor in a circuit?

<p>To change the value of current (D)</p> Signup and view all the answers

In the optics experiment, how is the pin at point O described?

<p>It is an optical object (A)</p> Signup and view all the answers

What type of graph should represent the relationship between voltage and current?

<p>A straight sloping line through the origin (C)</p> Signup and view all the answers

When light passes through a prism, which color of light is typically bent the least?

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

What is the combined resistance of resistors P and Q if their total resistance is 3 Ω?

<p>3 Ω (D)</p> Signup and view all the answers

What should you label at point P when drawing a normal to the mirror?

<p>Normal line (B)</p> Signup and view all the answers

Which of the following describes the condition under which the voltage across resistor R is low?

<p>The current through R is less than 2 A (C)</p> Signup and view all the answers

What is the distance of the image from your nose if your nose is 30 cm from the mirror?

<p>30 cm (B)</p> Signup and view all the answers

When using a rheostat, what should you do to obtain the desired current value?

<p>Close the switch before adjusting (B)</p> Signup and view all the answers

What marks the positions A and A’ on the beaker during the optics experiment?

<p>Points where the light enters and exits (D)</p> Signup and view all the answers

What type of contacts are needed for good electrical conductivity when using a slider?

<p>Good electrical contact (A)</p> Signup and view all the answers

If LP is a ray from the lamp, what is the purpose of marking equal angles at point P?

<p>To illustrate reflection properties (A)</p> Signup and view all the answers

What is the primary function of the mirror in Fig. 6?

<p>To reflect light to form an image (D)</p> Signup and view all the answers

What is the expected relationship between the potential difference (V) across a metallic conductor and the current (I) through it at constant temperature?

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

How can the resistance of a conductor be determined from the graph of current versus potential difference?

<p>By taking the slope of the line (B)</p> Signup and view all the answers

Given a wire with a specified resistance, how would you calculate the resistance per metre?

<p>By dividing the total resistance by the length of the wire (A)</p> Signup and view all the answers

If a laboratory technician requires a 64 Ω resistor, which calculation is necessary based on the resistance per metre?

<p>Divide 64 Ω by the resistance per metre (C)</p> Signup and view all the answers

What does a variable resistor allow you to do?

<p>Change the resistance within a specific range (D)</p> Signup and view all the answers

What is the significance of the pointer position on a variable resistor?

<p>It determines the specific resistance being used (D)</p> Signup and view all the answers

In a constant thickness wire, how does the resistance change when length is increased?

<p>Resistance increases (A)</p> Signup and view all the answers

Which of the following statements is true about the effects of the ammeter and voltmeter on the circuit?

<p>They have no effect on the circuit resistance (C)</p> Signup and view all the answers

What is the correct relationship between power input and power output in the given scenario?

<p>Power input equals power output. (A)</p> Signup and view all the answers

What happens to the current in cables when the voltage is increased?

<p>The current decreases substantially. (D)</p> Signup and view all the answers

If the current at point X is 3.1 A, what is the current at point Y?

<p>0.8 A (B)</p> Signup and view all the answers

What is the resistance of T if the voltage is 110 V and the current is 0.8 A?

<p>138 Ω (C)</p> Signup and view all the answers

How do you calculate the power if the voltage is 110 V and the current is 4.6 A?

<p>Power = Voltage × Current (B)</p> Signup and view all the answers

What is the final expression for energy converted if I is the current, R is resistance, and t is time?

<p>Energy = I^2Rt (D)</p> Signup and view all the answers

What would happen to the temperature of a body if the energy of its molecules is decreased?

<p>The temperature falls. (D)</p> Signup and view all the answers

Which substance would likely have the highest thermal capacity among various materials?

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

Why does the temperature of sand on a beach rise faster than that of the sea on a sunny day?

<p>Sand absorbs more sunlight than water. (C)</p> Signup and view all the answers

Which statement accurately reflects the process of evaporation?

<p>Evaporation occurs at the surface of the liquid. (C)</p> Signup and view all the answers

What is the role of higher energy molecules in the evaporation process?

<p>They escape from the surface of the liquid. (D)</p> Signup and view all the answers

How does rapid evaporation result in a cooling effect?

<p>It absorbs heat from the remaining liquid, lowering the temperature. (A)</p> Signup and view all the answers

Why might aftershave cool the skin better than water at room temperature?

<p>Aftershave contains substances that enhance evaporation. (D)</p> Signup and view all the answers

Which of the following statements about evaporation is false?

<p>Evaporation occurs at the bottom of the container. (A)</p> Signup and view all the answers

What happens to the temperature of a liquid during evaporation?

<p>It can drop due to the escaping high-energy molecules. (B)</p> Signup and view all the answers

What is a potential divider primarily used for in an electrical circuit?

<p>To divide voltage into smaller parts (D)</p> Signup and view all the answers

How does the polythene rod become negatively charged?

<p>By gaining electrons from the duster (B)</p> Signup and view all the answers

What happens to the metal plate when a negatively charged polythene rod is brought near it?

<p>Electrons move from the plate to the rod, charging the plate positively (A)</p> Signup and view all the answers

Which of the following best describes how a metal plate can become positively charged without direct contact with a negatively charged object?

<p>By induction where electrons move away from the plate (C)</p> Signup and view all the answers

In the context of the content, what is the role of the α-particle emitting source when brought close to the positively charged metal plate?

<p>To induce further charge separation in the plate (B)</p> Signup and view all the answers

What determines the output voltage ($V_{out}$) in a potential divider?

<p>The input voltage and the ratio of resistances (A)</p> Signup and view all the answers

What can be inferred about the nature of charging objects through friction?

<p>Frictional charging typically involves the transfer of electrons (A)</p> Signup and view all the answers

Which of the following statements is true regarding electron movement in static electricity?

<p>Electrons can accumulate and create a net charge in materials (A)</p> Signup and view all the answers

Flashcards

Refraction

The bending of light as it passes from one medium to another, for example from air to glass.

Normal

A line drawn perpendicular to the surface at the point where light strikes the surface.

Angle of incidence

The angle between the incident ray and the normal.

Angle of reflection

The angle between the reflected ray and the normal.

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Image

The apparent position of an object as seen by an observer, due to the bending of light rays.

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Focal point

A point where light rays from an object converge or appear to diverge.

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Thermocouple

A device used to detect infrared rays.

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Lens

A transparent object that bends light rays and can be used to form images.

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What is resistance?

The opposition to the flow of electric current in a conductor.

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What is the unit of resistance?

The unit of resistance is the ohm (Ω).

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What is a resistor?

A component in an electric circuit that has a fixed resistance.

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What is potential difference?

The potential difference across a component is the work done in moving a unit charge through it.

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What is the unit of potential difference?

The unit of potential difference is the volt (V).

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What is electric current?

The rate of flow of electric charge.

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What is the unit of current?

The unit of current is the ampere (A).

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What is Ohm's Law?

The relationship between potential difference, current and resistance is given by Ohm's Law: V = IR.

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Heat Transfer

The transfer of heat energy from a hotter object to a colder object.

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Conduction

The transfer of heat energy through direct contact between objects of different temperatures.

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Convection

The transfer of heat energy through the movement of fluids (liquids or gases).

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Radiation

The transfer of heat energy through electromagnetic waves, such as infrared radiation.

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Specific Heat Capacity

The amount of heat energy required to raise the temperature of 1 kg of a substance by 1 degree Celsius.

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Internal Energy

The total amount of energy in a system, including the kinetic energy of its molecules and the potential energy stored in its bonds.

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Heat Transfer Rate

The rate at which heat energy is transferred.

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Thermal Conductivity

The measure of the tendency of a material to conduct heat.

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p.d.

The potential difference (voltage) between two points in a circuit.

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What is the value of Vout?

The value of Vout depends on the ratio of the resistances in the potential divider. In this example, Vout = 1/2 of the supply voltage (as the resistors are equal).

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How does rubbing a polythene rod with a duster make it negatively charged?

Electrons are transferred from the duster to the polythene rod, giving the rod an excess of negative charge.

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How can a metal plate be positively charged without touching the negatively charged polythene rod?

The negatively charged polythene rod repels electrons in the metal plate, making it positively charged.

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What happens when a positively charged metal plate is brought near an alpha particle source?

An alpha particle is a positively charged particle. It is attracted to the positively charged metal plate.

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What is voltage?

Energy transferred per unit charge.

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Evaporation

Evaporation is the process where a liquid changes into a gas. It happens at any temperature, not just the boiling point. Molecules with higher energy escape from the liquid's surface, taking heat with them and causing cooling.

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Why does sand heat up faster than water?

The temperature of the sand on a beach rises faster than the sea because sand has a lower specific heat capacity. This means it takes less heat energy to raise the temperature of sand by a certain amount compared to water.

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What is Evaporation?

The molecules in a liquid are constantly moving and colliding with each other. Some molecules gain enough energy to escape from the liquid's surface and become gas molecules. This is called evaporation.

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Why does aftershave feel cooler than water?

Aftershave contains alcohol, which has a lower specific heat capacity than water. This means alcohol needs less heat energy to evaporate, making it feel cooler on the skin.

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Why does aftershave cool the skin?

The statement 'Rapid evaporation produces cooling' explains why aftershave cools the skin because the evaporation process removes heat energy from the skin, making it feel cooler.

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What is Specific Heat Capacity?

Specific heat capacity is the amount of heat energy needed to raise the temperature of 1 kg of a substance by 1 degree Celsius. Substances with lower specific heat capacities heat up faster than those with higher specific heat capacities.

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Why do higher energy molecules escape during evaporation?

The statement 'It is the higher energy molecules which escape' explains why aftershave cools the skin because the molecules with the highest energy levels are the ones that evaporate, removing heat energy from the skin.

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Why does alcohol evaporate faster than water?

Liquids with a lower specific heat capacity, like alcohol, require less energy to evaporate than those with a higher specific heat capacity, like water. Thus, alcohol evaporates more quickly and cools the skin faster.

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Description

Test your knowledge on fundamental concepts in electric circuits and optics. This quiz covers topics such as resistance calculation, properties of light, and component functions. Assess your understanding of these essential principles to excel in your physics studies.

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