أسئلة الفيزياء الصف الثامن مع الحل

15 سؤالاً تدريبياً في الفيزياء – الصف الثامن

1. الفصل: DC Voltage · سهل

   1. What is the voltage of three 1.5 V cells connected in series (+ to −)?

   • A. 1.5 V
   • B. 4.5 V
   • C. 3 V
   • D. 0.5 V
   أظهر الجواب ▾

   Answer: 4.5 V

   Explanation: Voltages add in series.

2. الفصل: DC Voltage · سهل

   2. A power line is at 5 kV. Express it in volts.

   • A. 500
   • B. 5000
   • C. 50
   • D. 5000000
   أظهر الجواب ▾

   Answer: 5000

   Explanation: 1 kV = 1 000 V → 5000 V.

3. الفصل: Alternating Voltage · سهل

   3. Oscilloscope sensitivity 1 V per division; the peak of the wave is 4 divisions above the middle line. Maximum voltage?

   • A. 3.5
   • B. 4.5
   • C. 5
   • D. 4
   أظهر الجواب ▾

   Answer: 4

   Explanation: U_max = 4 × 1 = 4 V.

4. الفصل: Alternating Voltage · سهل

   4. What is the period of an alternating voltage?

   • A. the number of cycles per second
   • B. the height of the wave
   • C. the duration of one complete cycle
   • D. the maximum voltage
   أظهر الجواب ▾

   Answer: the duration of one complete cycle

   Explanation: Measured in seconds.

5. الفصل: The Voltage of the Mains · سهل

   5. In a correct installation, what is the effective voltage between the live wire and the neutral wire?

   • A. 220
   • B. 0
   • C. 310
   • D. 110
   أظهر الجواب ▾

   Answer: 220

   Explanation: The live wire is at 220 V with respect to the ground and the neutral.

6. الفصل: The Voltage of the Mains · سهل

   6. In a correct installation, what is the effective voltage between the live wire and the earth wire?

   • A. 110
   • B. 310
   • C. 0
   • D. 220
   أظهر الجواب ▾

   Answer: 220

   Explanation: The live wire is at 220 V with respect to the ground and the neutral.

7. الفصل: Resistors · سهل

   7. What is the meaning of "milliampere"?

   • A. 1 mA = 0.001 A
   • B. the flow of electric charge through a component, measured in amperes with an ammeter in series
   • C. the property of a component that opposes the passage of current, measured in ohms
   • D. the possible deviation of the real value from the marked value (gold ±5 %, silver ±10 %)
   أظهر الجواب ▾

   Answer: 1 mA = 0.001 A

   Explanation: Milliampere: 1 mA = 0.001 A

8. الفصل: Resistors · سهل

   8. Resistors of 120 Ω and 20 Ω are connected in series. Equivalent resistance?

   • A. 17
   • B. 2400
   • C. 100
   • D. 140
   أظهر الجواب ▾

   Answer: 140

   Explanation: R = R₁ + R₂ = 120 + 20 = 140 Ω.

9. الفصل: Electric Power and Energy · سهل

   9. A 10 W lamp is on for 10 s. Energy consumed in joules?

   • A. 6000
   • B. 20
   • C. 100
   • D. 1
   أظهر الجواب ▾

   Answer: 100

   Explanation: E = P × t = 10 × 10 = 100 J.

10. الفصل: Electric Power and Energy · سهل

    10. Which term matches this definition: "the heating of a conductor by the current, with power P = R × I²"?

    • A. nominal power
    • B. Joule effect
    • C. standby
    • D. kilowatt-hour
    أظهر الجواب ▾

    Answer: Joule effect

    Explanation: Joule effect: the heating of a conductor by the current, with power P = R × I²

11. الفصل: Mechanical Actions · سهل

    11. A dynamometer reads 30 N with a schoolbag hanging from it. Mass of the object (g = 10 N/kg, a constant number)?

    • A. 6
    • B. 3
    • C. 2.5
    • D. 1
    أظهر الجواب ▾

    Answer: 3

    Explanation: m = W / g = 30 / 10 = 3 kg.

12. الفصل: Mechanical Actions · سهل

    12. A brick has a mass of 2 kg. Its weight (g = 10 N/kg, a constant number)?

    • A. 200
    • B. 25
    • C. 2
    • D. 20
    أظهر الجواب ▾

    Answer: 20

    Explanation: W = m × g = 2 × 10 = 20 N (g is a constant number, g = 10 N/kg).

13. الفصل: Equilibrium of a Body · سهل

    13. What is the meaning of "load"?

    • A. the force applied to a lever to move the load
    • B. the distance from the pivot to the line of action of a force
    • C. the object a lever lifts or the resisting force it overcomes
    • D. the state of a body at rest whose forces balance each other
    أظهر الجواب ▾

    Answer: the object a lever lifts or the resisting force it overcomes

    Explanation: Load: the object a lever lifts or the resisting force it overcomes

14. الفصل: Equilibrium of a Body · سهل

    14. A 5 kg box rests on the floor. Reaction of the floor on the box (g = 10 N/kg, a constant number)?

    • A. 100
    • B. 0
    • C. 50
    • D. 5
    أظهر الجواب ▾

    Answer: 50

    Explanation: R = W = 50 N, vertical, upwards.

15. الفصل: Pressure in Liquids · سهل

    15. Which term matches this definition: "the horizontal top surface of a liquid at rest"?

    • A. pascal
    • B. free surface
    • C. water tower
    • D. density (mass per volume)
    أظهر الجواب ▾

    Answer: free surface

    Explanation: Free surface: the horizontal top surface of a liquid at rest

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