PERCOBAAN 4

PEMBIASAN LENSA CEMBUNG

Tujuan : Menentukan titik focus lensa cembung dan menyelidiki sifat bayangan yang

dibentuk lensa cembung.

Alat dan bahan :

1. Lensa cembung2. Lampu3. Layar4. Preparat5. Power suplly6. Rel

Landasan teori :

Cermin cembung bersifat menyebarkan sinar. Berkas sinar sejajar sumbu utama dipantulkan menyebar seolah-olah berasal dari titik focus. Panjang focus sama dengan setengah jari-jari kelengkungan cermin. Sehingga didapat rumus :

1f= 1S+ 1S '

Cara kerja :

1. Susunlah alat – alat seperti gambar di atas.2. Geser lensa atau layar kekiri atau kekanan sehingga diperoleh bayangan

tjam pada layar.3. Ulangi kembali percobaan sehingga mendapatkan data S dan S’ yang

berbeda, kemudian catat datanya pada tabel.

Data – data percobaan

No S (cm) S’ (cm) 1/S 1/S’Titik focus

(f)1234

Pengolahan data :

1. Hitung titik focus (f)………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………..

2. Hitung titik fokus rata – rata

f= f 1+ f 2+ f 3+f 44

……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………..

3. Hitung simpangan rata – rata

∆ f=|f 1−f|+|f 2−f|+|f 3−f|+|f 4−f|

4……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………..

4. Ketelitian∆ ffx100 %

………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

5. Kesalahan percobaan

(1−∆ ff

) x100 %

………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….………………………………..………………………………………………………………………………………………………………………………………………………………………………………..

6. Kesimpulan ……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………..

PERCOBAAN 5

RANGKAIAN HAMBATAN SERI DAN PARALEL

Tujuan : Mengetahui besar hambatan total yang dirangkai seri dan besar hambatan total yang dirangkai paralel.

Alat dan bahan :

1. Hambatan/Resistor2. Kabel3. Multitester

Landasan Teori :

Untuk menghitung hambatan pengganti yang disusun secara seri dapat menggunakan rumus

RS = R1 + R2 + R3 + … + Rn

Untuk menghitung hambatan pengganti yang disusun secara paralel dapat menggunakan rumus

1RP

= 1R1

+ 1R2

+ 1R3

+…+ 1Rn

Cara kerja :

1. Ukur masing – masing hambatan dengan multitester dengan ukuran Ohmmeter.

2. Susunlah tiga hambatan secara seperti gambar di bawah ini secara seri dan ukur besar hambatan tersebut.

Data Percobaan

NoHambatan penyusun Hambatan Ukur

(Rs) Ʃ Hitung RsR1 R2 R3

1 Ω Ω Ω Ω Ω

Hitunglah a. Hambatan total dalam rangkaian seri!

………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

b. Kesalahan = |Rsukur−R shitungR shitung |x 100%

………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

c. Ketelitian = 1−|R sukur−RshitungR shitung |x100 %

………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………3. Susunlah tiga hambatan secara seperti gambar di bawah ini secara paralel

dan ukur besar hambatan tersebut.

Data percobaan

NoHambatan penyusun Hambatan Ukur

(Rp) Ʃ Hitung RpR1 R2 R3

1 Ω Ω Ω Ω Ω

Hitunglah a. Hambatan total dalam rangkaian seri!

…………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

b. Kesalahan = |Rpukur−RphitungRphitung |x100 %

…………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

c. Ketelitian = 1−|Rpukur−R phitungR phitung |x 100 %

…………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

Kesimpulan : …………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

……………………………………………………………………………………………………………………………………………………………………

PERCOBAAN 6HUKUM OHM

Tujuan : 1. Dapat menemukan hubungan antara tegangan kuat arus dan hambatan.2. Dapat menggambarkan grafik antara kuat arus dan tegangan penghantar.

Alat dan bahan :1. Power supply/ catu daya2. Hambatan geser3. Voltmeter4. Ampermeter

Landasan teori :Sebuah hambatan ujung-ujungnya dipasang tegangan V, pada penghantar akan mengalir arus listrik ( i ). Menurut hukum Ohm kuat arus yang mengalir pada suatu penghantar berbanding lurus dengan tegangan dan berbanding terbalik dengan hambatannya.Pernyataan itu di tulis dengan pernyataan :

i=VRatau V=i .Ratau R=V

iKeterangan :i : kuat arusV : teganganR : Hambatan

Langkah kerja :

1. Susun rangkaian seperti gambar di bawah ini

A : AmperemeterV : VoltmeterE : Tegangan sumberR : Hambatan

2. Ukuran hamabatan R dengan ohmmeter.

A

V

E

R

3. Hidupkan sumber tegangan atau catu daya dengan memilih tegangan keluaran 3 Volt.

4. Baca Ampermeter dan voltmeter dalam rangkaian.5. Ulangi percobaan 3 dan 4 dengan mengubah tegangan sumber sesuai data

pada tabel dibawah.

No. E (Volt) V(Volt) I(Amper) Hambatan (Ω)1. 32. 63. 9

Pengolahan data :

1. Hitung Hambatan ……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

2. Hitung hambatan rata – rata

R=R1+R2+R33

………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

………………………………………………………………………………………………………………………………………………………………

3. Hitung simpangan rata – rata

∆ R=|R1−R|+|R2−R|+|R3−R|

3……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………..

4. Ketelitian ∆ RRx 100 %

………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

5. Kesalahan percobaan

(1−∆ RR

)x 100 %

………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….………………………………..

…………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

6. Kesimpulan ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………