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Hingga ujian berikutnya 14–15 November 2026:
Semua konsep

Electric Field and Field Strength

电场与电场强度

Coulomb's law and charge conservation, the defining equation and superposition of electric field strength, the fields of a point charge and a uniform field, and what field-line density means.

16 soal ujian asli · 4 kali ujian22 soal tryout40 soal latihan

Ujian CSCA dikerjakan dalam bahasa Mandarin atau Inggris — peserta memilih sendiri. Karena itu konsep dan rumus di sini disajikan dalam kedua bahasa tersebut; halaman ini menampilkan versi bahasa Inggris.

Rumus

  • Coulomb's law

    Hukum
    F=kq1q2r2F=k\frac{q_1q_2}{r^2}

    Berlaku bila：Point charges in vacuum; k is the electrostatic constant

  • Definition of electric field strength

    Definisi
    E=FqE=\frac{F}{q}

    Berlaku bila：A ratio definition: E is set by the field itself, not by the test charge q

  • Field of a point charge

    Rumus
    E=kQr2E=k\frac{Q}{r^2}

    Berlaku bila：A point charge in vacuum. Outside a uniformly charged shell or solid sphere the field is the same as if all the charge sat at the centre; inside they differ — the field is zero inside a shell (and inside a conductor in electrostatic equilibrium), but not inside a uniformly charged solid sphere

  • Field strength in a uniform field

    Rumus
    E=UdE=\frac{U}{d}

    Berlaku bila：Uniform fields only; d is measured along the field direction

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Soal dari ujian CSCA sebenarnya yang menguji konsep ini. Kerjakan sendiri dulu sebelum membuka jawabannya.

  1. CSCA Physics December 2025 Past Paper
    The electric field lines of an electric field are distributed as shown in the figure. If point charges aa and bb of equal charge are placed at points a and b in the field, the relationship between the electric forces exerted on the two point charges is ( ), Question 25 diagram
    • A．Fa≥FbF _ { a } \geq F _ { b }
    • B．Fa=FbF _ { a } = F _ { b }
    • C．Fa<FbF _ { a } < F _ { b }
    • D．Fa>FbF _ { a } > F _ { b }
    Lihat jawaban & pembahasan

    Jawaban: C

    1 Electric force on a test charge: F=qEF = q E. 2 Field strength is larger where field lines are denser; point bb is in the denser region than point a (from the diagram). 3 So FbF_b > FaF_a, i.e., FaF_a<FbF_b.
    Lihat di CSCA Physics December 2025 Past Paper lengkap
  2. CSCA Physics March 2026 Past Paper
    Charges A,B,C\mathrm { A } , \mathrm { B } , \mathrm { C } at vertices of an equilateral triangle. A and B are positive. The resultant force on A from B and C is F_A\mathrm { F } \_ \mathrm { A }, with angle to BA extension <60∘< 60 ^ { \circ }. Which is correct about C ? Question 29 diagram
    • A．Positive, charge < B
    • B．Negative, charge >B> B
    • C．Positive, charge > B
    • D．Negative, charge < B
    Lihat jawaban & pembahasan

    Jawaban: D

    BB repels AA along BAB A extension. Resultant angle <60∘< 60 ^ { \circ } means slight deflection toward CAC A. If CC were positive, its repulsion would push the angle beyond 60∘60 ^ { \circ } - contradiction. So C is negative (attractive), deflecting toward CA．Angle <60∘< 60 ^ { \circ } means C 's attraction <B< \mathrm { B } 's repulsion, so ∣C∣<∣B∣| \mathrm { C } | < | \mathrm { B } |. Answer: D．
    Kerjakan CSCA Physics March 2026 Past Paper lengkap — berwaktu & dinilai
  3. CSCA Physics April 2026 Past Paper
    A point charge QQ produces an electric field of magnitude EE at point AA. If the distance from the charge to AA is doubled, the new electric field magnitude is
    • A．E2\frac { E } { 2 }
    • B．2E2 E
    • C．E4\frac { E } { 4 }
    • D．4E4 E
    Lihat jawaban & pembahasan

    Jawaban: C

    Since E=kQr2,EE = \frac { k Q } { r ^ { 2 } } , E is inversely proportional to r2r ^ { 2 }. Doubling rr reduces EE to 14\frac { 1 } { 4 } of its original value.
    Kerjakan CSCA Physics April 2026 Past Paper lengkap — berwaktu & dinilai

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Konsep terkait

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