JAWABAN UJI KOMPETENSI LISTRIK STATIS KELAS XII IPA1

KODE SOAL : A

1. Q = 8 . 10^-9 C

a) pada r₁ = 20 cm Þ V₁ = k Q/r₁ = 360 Volt

pada r₂ = 40 cm Þ V₂ = k Q/r₂ = 180 Volt

b) W₂₁ = q’ . DV₁₂ = 5 . 10^-8 (180 – 360) = - 9 . 10^-6 J

2. F₁ = F₁₂ + F₁₃

= k (q₂.q₁)/r₁² + k (q₁.q₃)/r₂²

= 5,832 . 10^-6 N (arah resultan gaya ke kanan)

3. C_pengganti = 3 mF + 4 mF + 5 mF = 12 mF.

a) Q₁ = C₁ . V = 270 mC

Q₂ = C₂ . V = 360 mC

Q₃ = C₃ . V = 450 mC

b) V₁ = V₂ = V₃ = V = 90 V

c) W = ½ CV² = 486 . 10^-4 J

4. q₁/r₁² = q₂/r₂²

Þ 9/(6 + x)² = 4/x²

Þ 9/4 = (6 + x)² / x²

Þ3/2 = (6 + x) / x

3x = 2(6 + x)

x = 12 cm di sebelah kanan muatan 4 nC.

5. r = 5 cm

q = 6 . 10^-5 C

a) s = q/(4pr²) = (6/p) . 10^-3 C/m²

b) pada r = 5 cm Þ E₁ = kq/r₁² = 2,16 . 10⁸ N/C

pada r = 10 cm Þ E₂ = kq/r₂² = 54 . 10⁶ N/C

KODE SOAL : B

1. F₁ = F₁₂ + F₁₃

= k (q₂.q₁)/r₁² - k (q₁.q₃)/r₂²

= 2,511 N (arah resultan gaya ke kanan)

2. q₁/r₁² = q₂/r₂²

Þ 2/(x)² = 32/(8 + x)²

Þ 2/32 = x²/(8 + x)²

Þ 1/4 = x / (8 + x)

8 + x = 4x

x = 8/3 cm = 2,67 cm di sebelah kiri muatan 2 nC.

3. Q = 4 . 10^-6 C

a) pada r₁ = 40 cm Þ V₁ = k Q/r₁ = 9 . 10⁴ Volt

pada r₂ = 20 cm Þ V₂ = k Q/r₂ = 18 . 10⁴ Volt

b) W₁₂ = q’ . DV₂₁ = 4 . 10^-8 (-9 . 10⁴ Volt) = - 36 . 10⁴ J

4. r = 10 cm

q = 5 . 10^-8 C

a) s = q/(4pr²) = (1,25/p) . 10^-6 C/m²

b) pada r = 5 cm Þ E₁ = 0

pada r = 20 cm Þ E₂ = kq/r₂² = 1,125 . 10⁴ N/C

5. C_pengganti = 60/47 nF

a) Q₁ = Q₂ = Q₃ = Q = C_s . V = 60/47 nF . 100 V = 127,66 nC

b) V₁ = Q/C₁ = 42,55 V

V₂ = Q/C₂ = 31,91 V

V₃ = Q/C₃ = 25,53 V

c) W = ½ CV² = ½ . (60/47) . 10^-9 . 100² = 6,38 . 10^-6 J