Section 3: Hydraulic Jack Questions
3.2.1 Define the term pressure
Pressure is defined as the force applied per unit area. Mathematically, it is expressed as:
\[ \text{Pressure} (P) = \frac{\text{Force} (F)}{\text{Area} (A)} \]
(1 mark)
3.2.2 Calculate the pressure produced by piston A on the oil.
Given:
- Force \( F = 40 , \text{N} \)
- Area \( A = 0.010 , \text{m}^2 \)
Using the formula for pressure:
\[ P = \frac{F}{A} = \frac{40 , \text{N}}{0.010 , \text{m}^2} = 4000 , \text{Pa} \]
(2 marks)
3.2.3 State the pressure on piston B when the pistons stop moving. Explain your answer.
The pressure on piston B when the pistons stop moving is 4000 Pa.
Explanation: According to Pascal's principle, when pressure is applied to a confined fluid, that pressure is transmitted undiminished in all directions throughout the fluid. Therefore, the pressure exerted on piston A is equal to the pressure exerted on piston B when the system reaches equilibrium and stops moving.
(2 marks)
3.3 Give two factors that affect liquid pressure.
- Depth of the liquid: The deeper the liquid, the greater the pressure due to the weight of the liquid above.
- Density of the liquid: The greater the density of the liquid, the higher the pressure at a given depth, due to the weight of the liquid column. (2 marks)
Section D: Long Questions
1.1 Name the type of connection in circuit 2.
Circuit 2 shows a parallel connection.
(1 mark)
1.2 State two advantages of connecting the lamps as shown in circuit 2.
- Independent Operation: If one lamp fails, the other lamp will still operate.
- Increased Brightness: Each lamp receives the full voltage of the power supply, resulting in brighter lamps compared to a series connection. (2 marks)
1.3 Calculate the ammeter reading shown in circuit 1 when the switch is closed.
*In circuit 1 (e.g., in series), the total resistance \( R_t \) is:
\[ R_t = R_1 + R_2 = 3 , \Omega + 5 , \Omega = 8 , \Omega \]
Assuming the circuit is powered by a voltage \( V \) (not provided in the question, for calculation let's use \( V = 24 , \text{V} \) as an example):
Using Ohm’s Law:
\[ I = \frac{V}{R_t} = \frac{24 , \text{V}}{8 , \Omega} = 3 , \text{A} \]
(3 marks)
(Note: The actual voltage value must be known for the precise ammeter reading.)
1.4 Calculate the combined resistance of the lamps in circuit 2 when both switches are closed.
For lamps in parallel, the total resistance \( R_t \) can be calculated via:
\[ \frac{1}{R_t} = \frac{1}{R_1} + \frac{1}{R_2} = \frac{1}{3 , \Omega} + \frac{1}{5 , \Omega} \]
Finding a common denominator (15):
\[ \frac{1}{R_t} = \frac{5}{15} + \frac{3}{15} = \frac{8}{15} \]
So:
\[ R_t = \frac{15}{8} , \Omega \approx 1.875 , \Omega \]
(2 marks)
2.1 Identify the type of motor represented in Fig. 2.1.
The type of motor is a DC motor.
(1 mark)
2.2 State two ways in which the speed of rotation of the coil can be increased in the motor in Fig. 2.1.
- Increase the current flowing through the coil: This increases the magnetic field strength and hence the torque.
- Increase the number of turns in the coil: More turns increase the induced emf and thus increase the motor speed. (2 marks)
2.3 Briefly explain how an e.m.f is generated in the coil when the coil is rotated.
An e.m.f (electromotive force) is generated in the coil due to the principle of electromagnetic induction, which states that a changing magnetic field through a coil induces a voltage. When the coil is rotated in a magnetic field, the magnetic flux through the coil changes, which, according to Faraday's Law of Induction, induces an e.m.f in the coil. The induced e.m.f is proportional to the rate of change of the magnetic flux through the coil.
(2 marks)
This concludes the entire question set with explanations, calculations, and answers.
3 answers