Nursing Elites

1. What is the purpose of a switch in a circuit?

• A. To reverse the direction of alternating current
• B. To increase the voltage of the battery or cell
• C. To increase the resistance of wires in the circuit
• D. To allow the circuit to open and close

Correct answer: D

Rationale: The purpose of a switch in a circuit is to allow the circuit to open and close. When the switch is turned on, it provides a complete path for the current to flow through the circuit. When the switch is turned off, it breaks the circuit, stopping the flow of current. This function of opening and closing the circuit using a switch is essential for controlling the flow of electricity in various electrical devices and systems. Choices A, B, and C are incorrect because a switch does not reverse the direction of current, increase voltage, or increase resistance in a circuit; its primary function is to open and close the circuit.

2. A 110-volt appliance draws 0 amperes. How many watts of power does it require?

• A. 0 watts
• B. 108 watts
• C. 112 watts
• D. 220 watts

Correct answer: A

Rationale: When a 110-volt appliance draws 0 amperes, it means that the power consumption is zero as well. The formula to calculate power is P = V x I, where P is power in watts, V is voltage in volts, and I is current in amperes. Since the current is 0 amperes, the power required by the appliance is also 0 watts. Therefore, the correct answer is 0 watts. Choice B, 108 watts, is incorrect because there is no current drawn. Choice C, 112 watts, and choice D, 220 watts, are incorrect as well since the appliance is not consuming any power when drawing 0 amperes.

3. The Prandtl number (Pr) is a dimensionless property relating:

• A. Viscosity and thermal diffusivity
• B. Density and pressure
• C. Surface tension and pressure
• D. Reynolds number and flow regime

Correct answer: A

Rationale: The Prandtl number (Pr) is a dimensionless number used to characterize fluid flow. It is the ratio of momentum diffusivity to thermal diffusivity. In simpler terms, it relates the ability of a fluid to conduct heat to its ability to conduct momentum. Therefore, the correct relationship is between viscosity and thermal diffusivity, making choice A the correct answer. Choices B, C, and D are incorrect because they do not represent the properties that the Prandtl number relates.

4. The buoyant force, F_b, experienced by an object submerged in a fluid is given by:

• A. F_b = W, the object's weight
• B. F_b = W_d, the weight of the fluid displaced by the object
• C. F_b = ρ, the density of the fluid
• D. F_b = V, the object's volume

Correct answer: B

Rationale: The correct formula for the buoyant force experienced by an object submerged in a fluid is given by Archimedes' principle, which states that the buoyant force is equal to the weight of the fluid displaced by the object. This is represented by the formula F_b = W_d, where W_d is the weight of the fluid displaced by the object. This force acts in the opposite direction to gravity and is responsible for objects floating or sinking in fluids. Choice A is incorrect because the buoyant force is not equal to the object's weight. Choice C is incorrect because the density of the fluid is not directly related to the buoyant force. Choice D is incorrect because the object's volume is not the determining factor for the buoyant force.

5. In open-channel flow, a critical property is the free surface, which refers to the:

• A. Interface between the liquid and the container walls
• B. Interface between the liquid and a surrounding gas
• C. Bottom of the channel
• D. Region of highest velocity within the liquid

Correct answer: B

Rationale: The free surface in open-channel flow refers to the interface between the liquid and the surrounding gas, typically the atmosphere. This interface is critical as it determines the boundary between the liquid flow and the open environment. Option A is incorrect as it refers to the liquid-container wall interface, not the free surface. Option C is incorrect because it represents the bottom of the channel, not the free surface. Option D is incorrect as it describes the region of highest velocity within the liquid, not the free surface. Therefore, the correct choice is B.

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