​i have two questions on 18th jan 2018 (1) scum (2) normal and abnormal conditions of ECG
​i have got the answer for the (1) it is from chemistry not from biology (2) i have got answer for normal one not abnormal conditions  please 

Dear student

Please refer the solution below for the said query

1. 
The material that floats on top of the clarified water in a sedimentation tank during primary treatment of sewage, is known as scum.  

2.

Electrocardiogram is graphical representation of the activity of the heart during a cardiac cycle. 

• Each peak of the electrocardiogram corresponds to a specific electrical cardiac activity.

• Waves of a normal/standard electrocardiogram:

  • P wave − electrical depolarisation of the atria, leading to atrial systole

  • QRS complex − electrical depolarisation of the ventricles, leading to ventricular systole

  • T wave − electrical repolarisation of the ventricles, marking the end of systole

• Number of QRS complexes = Rate of heart beat

Normal condition of ECG: The normal condition of ECG is explained by the following shape of the graph. ​​

Abnormal condition of ECG:

Any deviation from the standard shape of an ECG graph indicates a disease or abnormality. This deviation may be due to the myocardial infarction (heart attack), arrhythmia etc. The abnormal condition of ECG is explained by the following shape of the graph. ​​

Hope this information clears your doubt about the topic.

Regards