Diketahui:
![](https://imgix2.ruangguru.com/assets/miscellaneous/png_7inmkf_4991.png)
![I subscript 1 equals I subscript 2 equals I](data:image/png;base64,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)
Ditanya:
![B subscript P equals... ?](data:image/png;base64,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)
Penyelesaian:
Medan magnet pada titik P (titik di tengah-tengah antara kedua kawat) merupakan hasil superposisi medan magnet yang dihasilkan oleh arus listrik pada kawat pertama dan kedua. Langkah pertama, hitung terlebih dahulu jarak titik P ke masing-masing kawat. Titik P berada di tengah-tengah antara kedua kawat, sehingga nilai
adalah sebagai berikut:
![a subscript 1 equals a subscript 2 equals 1 half a a subscript 1 equals a subscript 2 equals a over 2](data:image/png;base64,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)
Selanjutnya hitung B1 dan B2 di titik P, yaitu:
![B subscript 1 equals fraction numerator mu subscript 0 times I subscript 1 over denominator 2 pi times a subscript 1 end fraction B subscript 1 equals fraction numerator mu subscript 0 times I over denominator 2 pi times begin display style a over 2 end style end fraction B subscript 1 equals fraction numerator mu subscript 0 times I over denominator pi times begin display style a end style end fraction](data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAFEAAACcCAYAAAAH+UdcAAAACXBIWXMAAA7EAAAOxAGVKw4bAAAABGJhU0UAAABPJkfOnwAABHhJREFUeNrtnDFoFEEUhocjhEPSpBCREGzEQsROgkiwSSFBQkgjFhIkECysRBALEQvBQkQkCCIiFhKQYBFEBBGLFGInQUQCV1geQggiIkE43+A7six73szO29ndt/8HP9wNe3PcY3dn3tt7vzEAAAAAEGeB9BxhCOMm6RrCEMYL0rz2H/mVNOkw9j+WWFlskSY0B7BF+uUwNoweywjMVTumSO8dxiTnV8c50rPU2HnSU6H5JeeqLPdJl1Jjq6Tl1Ngk39t875UPMuY6qe3sfEm6x6+PkNZI30mzqeMekS7y4vHQc/70XO8G3D9riw3YZ9Iu6SNphtQltVPHfeOxUX7tynbGXEZTEG1AdhyP3R3wOi9qgjjLlxuCGMAi3/hd6F/OY56Xs/og+rDCC8uy58IiGsQF/uAf0m/SD17x2jUJ4kFShzUhEMBenkDaSsbV1L5rkzejwKOSMZcae81pEXBkiy8Jm5Af50zhSsBlkCXVtPhe2P+xdjN7CudV/kqGPRtv8E7+cKTv79VUQysZKxxMXM4elYyljCBe0FzZKKJScoZftznJt0n/fs2VDWm2E5ec3Wi/JR1DKlTcAgAqHsSzpA2uwmxwDjyGIPrxinSa962GF7s1BDE8Cch6nLnI44O2UqOe33OAtM7rQZd3IoVviGNxiKsyaW7zzqFj9h5KdThRGMSgh/f7SF/Mv6eKluuprV3tsWfHvMNZOkL66XgSpLH1gbuJ94+Nkr+U2MXE/ktrzjFVDUkE7OemE+/fkE7UPYD2/rTqkLcnU9WQB/A7iYWsf3a36hzAcc6exh2OXUnc4+xz6cs5v/OT2aveT3HikaZWKe/6gEwpi83EZfeEdMfke5RxiwstLa4hdDOOqVXK61r9mebcvs8Mb0/y/FFzhFdkG8CjpA8m+5EIsjXPoLYQRNQNEEQEEVQq5QUAAAAAAAAAUAjowhcAXfgCoAvfEXThO4wNA134DmOS86sDXfgClNGFr44yuvDVUVYXvhrK7MJXQ5ld+Gooswu/kUh34XtVL+rceZ9Esgvfu3qBznuB6gU67wNB571AdQSd94LVC3Teo/O+PNB5L1QdQed9IOi8jwiCiCAiiLEovIFcexALbyBvwn5PbQN5TFQ2kMdGXQN5Gbg0kIMhuDSQgyG4NpBXmqrZXI3U8Z7YCJur2MSyuVJNDJsr9cSwuVJLTJsrYwKeq1SV2DZX6ijD5krlPTC2zZU6yrC5AgBpp0qQdkZMO4FA2gmE0k4gkHYCgbQTCKSdQCDtBIFpJwAAAAAAAACAygKTSQFgMikATCYdgcmkw9gwYDLpMCY5vzpgMikATCYFgMmkADCZDAQmkwLAZFIAmExGpjSTSZfqRl1MKEszmXSpbsCEUqC6ARPKQGBCKVA9gQmlYHWjaSaUYsCEUgCYUApVT2BCGQhMKCOCICKICCKC6IG0503hzpx594BFIul5U7gzZ9XTUAnPm0Y7c0p53jTamVPK86bRzpxSnjeNduaU8rxprDOnpOeNCmfOqlGIM+dfvv+IWWSBKDoAAANVdEVYdE1hdGhNTAA8bWF0aCB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMTk5OC9NYXRoL01hdGhNTCI+PG1zdWI+PG1pPkI8L21pPjxtbj4xPC9tbj48L21zdWI+PG1vPj08L21vPjxtZnJhYz48bXJvdz48bXN1Yj48bWk+JiN4M0JDOzwvbWk+PG1uPjA8L21uPjwvbXN1Yj48bW8+JiN4Qjc7PC9tbz48bXN1Yj48bWk+STwvbWk+PG1uPjE8L21uPjwvbXN1Yj48L21yb3c+PG1yb3c+PG1uPjI8L21uPjxtaT4mI3gzQzA7PC9taT48bW8+JiN4Qjc7PC9tbz48bXN1Yj48bWk+YTwvbWk+PG1uPjE8L21uPjwvbXN1Yj48L21yb3c+PC9tZnJhYz48bXNwYWNlIGxpbmVicmVhaz0ibmV3bGluZSIvPjxtc3ViPjxtaT5CPC9taT48bW4+MTwvbW4+PC9tc3ViPjxtbz49PC9tbz48bWZyYWM+PG1yb3c+PG1zdWI+PG1pPiYjeDNCQzs8L21pPjxtbj4wPC9tbj48L21zdWI+PG1vPiYjeEI3OzwvbW8+PG1pPkk8L21pPjwvbXJvdz48bXJvdz48bW4+MjwvbW4+PG1pPiYjeDNDMDs8L21pPjxtbz4mI3hCNzs8L21vPjxtc3R5bGUgZGlzcGxheXN0eWxlPSJ0cnVlIj48bWZyYWM+PG1pPmE8L21pPjxtbj4yPC9tbj48L21mcmFjPjwvbXN0eWxlPjwvbXJvdz48L21mcmFjPjxtc3BhY2UgbGluZWJyZWFrPSJuZXdsaW5lIi8+PG1zdWI+PG1pPkI8L21pPjxtbj4xPC9tbj48L21zdWI+PG1vPj08L21vPjxtZnJhYz48bXJvdz48bXN1Yj48bWk+JiN4M0JDOzwvbWk+PG1uPjA8L21uPjwvbXN1Yj48bW8+JiN4Qjc7PC9tbz48bWk+STwvbWk+PC9tcm93Pjxtcm93PjxtaT4mI3gzQzA7PC9taT48bW8+JiN4Qjc7PC9tbz48bXN0eWxlIGRpc3BsYXlzdHlsZT0idHJ1ZSI+PG1pPmE8L21pPjwvbXN0eWxlPjwvbXJvdz48L21mcmFjPjwvbWF0aD6Zb/v0AAAAAElFTkSuQmCC)
Selanjutnya menentukan arah medan magnet B1 dan B2 di titik P menggunakan kaidah tangan kanan, yaitu:
![](https://imgix2.ruangguru.com/assets/miscellaneous/png_xwwtlj_2015.png)
Pada gambar itu terlihat bahwa arah B1 dan B2 adalah sama, yaitu masuk bidang yang ditandai dengan tanda silang. Selain menggunakan kaidah tangan kanan seperti gambar di atas, kita bisa memastikan bahwa jika arah arus kedua kawat berlawanan arah seperti pada soal ini, maka medan magnet B1 dan B2 yang berada di antara kedua kawat memiliki arah yang sama. Sehingga, karena arah medan magnet B1 dan B2 di titik P adalah sama, maka keduanya saling menguatkan, yaitu:
Besar induksi magnetik di tengah-tengah antara kedua kawat adalah ![fraction numerator bold 2 bold italic mu subscript bold 0 bold italic I over denominator bold italic pi bold italic a end fraction](data:image/png;base64,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)
Jadi, pilihan jawaban yang tepat adalah D